is it important to Sync my iPhone?

1. Transfers all purchased media (music, apps, books, etc.) and othe data (notes, voice memos, etc.) on your phone to your computer (iTunes library) for safekeeping; creates an updated backup of your phone everytime you sync; allows you to sync data on your computer to your phone if your computer is not syncing with iCloud (such as contacts, calendars, photos); provides the only way to restore your phone if you ever need to.

2. Depends on how you define "bad". You would lose all the benefits of syncing above.

3. No.

Syncing is important for all the reasons randers4 mentioned.

One other reason is if you break your phone and get a replacement

or want to upgrade, all synced information in maintained and can

be transfered to the new phone.

Of course you need to sync. While iCloud eliminated the requirement for a computer when using an iPhone, syncing is a must. You either backup/sync with iCloud or directly with a computer. If you don't want to do that, you will eventually lose all of your data. So, its not a question of good vs bad, fact is syncing is a requirement.

Syncing also means a backing up, so with a backup you can restore whenever there's a problem on you iPhone.

It is not a must but it's always safer and is encourage to have a backup.