Why do I have 7 UserID Aliases?

Either I don't understand your question (which is likely) or you didn't understand my answer, and I don't know how to explain it any better than I did.

If you believe redundant IDs exist, you can delete them if you wish, but be sure to heed the warning on that dialog box:

I wouldn't wish iCloud problems on anyone. They can be difficult or impossible to fix without Apple's intervention.

In any event you should probably contact Apple Support regarding concerns with Apple IDs that you may have: Contact Support. Any further diagnosis would require that you divulge information that you probably ought not to divulge on a publicly accessible website like this one.

If your Apple ID differs from your iCloud ID or iTunes ID, that would explain the number of aliases. I wouldn't delete any of them. Although it is simpler to have just one Apple ID for all the Apple products and services you use, aliases are created for your convenience.

I would recommend using Two-factor authentication for Apple ID - Apple Support. That prevents unauthorized use of your Apple ID.

If you should ever lose your MacBook, you can remotely lock it: If your Mac is lost or stolen - Apple Support.

Otherwise, your Mac's security is as good as the passwords you use to protect it. FileVault will make its storage inaccessible, and a firmware password will make the rest of its hardware totally useless to anyone without those passwords.

My fear is that someone can steal my laptop and then social engineer Apple to get my AppleID PW and login to it.

Apple is fully aware of that possibility, and is not likely to succumb to such tactics. It can be a significant problem for people who have legitimate claim to their own Apple ID credentials. Apple will refuse to help and they make that abundantly clear in their support documentation:

Can Apple Support help me regain access to my account?

Apple Support can answer your questions about the account recovery process, but can't verify your identity or expedite the process in any way.

I can't explain the purpose of it being associated in you User ID, but what you are seeing is normal. Any iCloud ID you use while logged into that account will be automatically associated to your User Account. It only shows in the Advanced Options of your account. Possibly you may have old IDs not used anymore which could be removed, but I would leave things as is.

As John said, head the warning.

If you wish to pursue it and delete some of them, just be sure to have good backups of your system where you can restore it in the event of problems occurring.

I have a question for you: why would you allow access to your ID and password to anyone else? I certainly wouldn't - ever. If you wish to allow access to someone else, why not set up another user account or a guest account for that matter? You can control what access they'd have.

As to your aliases, I looked into mine. I had 8 aliases shown. The first 2 were for my wife's apple id and a login certificate under each of her id names. The certificates are the ones named com.apple.idms.appleid.prd.************. At one time, I had logged into my wife apple id in iCloud account to test some things out. I assume it was then when they got associated to my account. After checking Keychain and viewing the certificates, 2 (her's) were out of date. I deleted her aliases and certificates from my account & Keychain. It didn't affect anything.

I suggest you don't delete any alias (which would be the same as your apple IDs) or the certificate under each of the valid id names. That would probably cause issues with any active iCloud services you are using.

Not knowing the purpose of this association for sure, I would assume it has something to do with tying your keychain together with your user account for iCloud services. You can also use your Apple ID to recover your computer password, which is another reason for the association.

Even though they are associated with your account, you can't log into your computer with them unless you had set it up that way.

I see; I just checked mine and only have one listed which is my old Apple ID email address. I changed that because that online email provider informed me that my free account would be terminated as they were changing to a paid model - so I got a different email address. Oddly enough, that is not listed under aliases.

In any case, I am wondering if I can safely remove that outdated email address since it is going to go "poof" in about a month anyway.

If you no longer use it and disassociated it from your Apple ID, then you should remove it from your user account. To be sure, you should log on the the manage apple id site and verify that it is no longer used. If you haven't removed it there, you should do so.

I never really looked into this, but I got curious. Just googled and came up with this which gives a bit of explanation to what they can do. I'm going to have to look a bit more for a better understanding on all the things it can do.

https://www.macobserver.com/tmo/article/mac_os_x_adding_account_aliases/

http://osxdaily.com/2011/05/22/setup-user-name-alias-mac/

Interesting articles - thanks for the links. I did check my Apple ID and it was still listed there (why I do not know since my Apple ID email was changed); in any case, I deleted it there and will delete it on my Mac as well. I don't think I need an alias here at all as I am the only one who accesses/uses the devices - he's got his own and I don't use his either ("his" and "hers" MBPs, iPads, etc). As as aside, we're actually just now both working on a "digital management" of devices/passwords list to keep in an accessible place just in case, so we have access and can log in/delete/whatever in case of a life/death/serious emergency situation.

I never manually added aliases to my account either. Besides creating your own alias for the purposes suggested in those articles, I assume the apple ids are added to your user account when you log into specific iCloud services. So there may be other functions to this other than what the articles say. I hadn't found exactly why the apple id was added or when. On my wife's computer, only one of her iCloud address are shown. Likely because we only use that one to log into her iCloud system. On my computer, I use both of my address associated with my apple id to log into iCloud services, and they all showed up in there, including my wife's id. As I said, I log into her account from time to time on my computer when I need to.

So, even if you delete everything in the list, it may come back one day if you use iCloud services.

As far as for using the aliases to log into certain access on the computer, I did not know that until today. Of course, you can't use them to log onto the computer since they don't show up in the user list.

Unless you have set your computer to log in with your iCloud ID, it can't be done. Only your user account will show up in the login screen. The aliases to the account won't show in the list to select them. The password for the user account and aliases will be the same.

So, even if you delete everything in the list, it may come back one day if you use iCloud services.

Well, then it shouldn't since I've chosen not to use any iCloud services. I do not trust any online server with any of my information. I do have an icloud email (established some time ago for testing purposes), but I only check it occasionally via a browser.

Well maybe in your case, it won't come back.

As to how your id got there, since you have an iCloud email, then you have logged into iCloud at some point. That's probably how it got associated to your user account. If you no longer log into iCloud for any reason, then yours shouldn't come back.

And for trusting any online server, if you have an email account even outside of Apple, then you have already trusted an online server with your information.

And just to say, I don't understand the compulsion people have to not use iCloud services. I see many say the same thing, but to my amazement they use Yahoo & Google accounts with calendars and address books, as well as other online sites.

As far as iCloud services, I trust Apple's security more than I trust Yahoo or any other services provider out there. I don't necessarily have all services enabled, but the ones I do use function very well compared to any other sites I've tried, such as google calendar.

And for everyone out there with a portable mac or iOS device, I can't imagine how you would not enable iCloud services even if were only to use Find My Mac for security purposes in case it's lost or stolen.