How to disable / turn off Verizon Backup Assistant without a factory reset
(and Use gmail contacts sync only - recommended!)
Also in post #3 below: How to Sync Contacts with Gmail and Change Contact type from Phone to Google
Disabling Backup Assistant on the HTC Droid Incredible
There may be other ways to disable backup assistant, but follow these steps to remove duplicate contacts and backup assistant without having to factory reset. Please be aware that I just tinkered around until I got the desired result. I'm no expert and I have no idea if this effects the phone in any other way. I did this over the weekend and everything is working perfectly on my phone. So proceed at your own risk, I don't want to get any pm's about how your phone blew up. I'm just trying to help out here.
1) Be sure to have all your contacts backed up to your Gmail account. Check online before proceeding to step 2.
2) Log into your My Verizon account. Go to the contacts tab, sort by list view and select all contacts. Delete the entire list. There's a deleted contacts tab as well. Select that and delete anything that's in there.
3) Go into your Incredible settings tab, select applications, manage applications. Do not sort or filter, allow list to populate. Select Sync Service, (icon resembles backup assistant icon) select clear data.
4) Also in manage applications scroll down to backup assistant, select clear data. This should do it.
5) To verify backup assistant is now disabled, select settings, accounts and sync, then under manage accounts, select backup assistant. You should be looking at a license agreement screen.
No more backup assistant, no factory reset.
The Android Blog
Source: Disabling Backup Assistant on the HTC Droid Incredible
If you're rooted, you can use the free "Titanium Backup" to uninstall Backup Assistant. Be sure to back it up in Titanium backup before uninstalling it. After you uninstall, it will no longer appear at all in Accounts and Sync.