RE: Time Machine - cam a cloud backup source be used? Or do you have to use an external hard drive? And how can you tell how much data you have to back up with the Time Machine so I know how large of a drive I need?
Time Machine is really designed to use an attached disk or an Apple Time Capsule in your home. It could also go to a local NAS (Network Attached Storage) in your home, but Apple most likely does not officially support that (your mileage may vary). Talking to a cloud storage system would require the cloud storage looking like a networked mounted volume.
However, I think you would be better served using a commercial cloud backup service, such as CrashPlan, Mozy, Carbonite, SugarSync, etc... For limited backup, so people use services such as Dropbox, or similar single folder file syncing service.
NOTE: CrashPlan can be used for free to backup across the internet (or even within your home) between 2 systems you control, or between you and a friend/family member. You put some storage on a system at the other location, and you both run CrashPlan having your copy send your backup data to the other system. If you are really nice, you let them put some storage on your system and they send their backups to your house. The files are encrypted locally and the data is transferred and stored encrypted so the other person does not have access to your data contents unless you give them the encryption keys.
Time Machine - can I backup to a cloud storage site?
