Contact sync is scary
So what the Nexus One did was decide that my device was the Master, and the Gmail server hosting all of my contacts should be overwritten with this master content. [..] I had 5 years worth of contacts in my gmail, from so many projects and encompassing so many people I’ve met and done work with.
Alfie lost his GMail contacts. I feel for him; contact (and calendar) sync can be magic, annoying (because now you have two of everything) or _lethal_, because everything is suddenly gone, and there's no undo. But there's an important lesson here. Back things up. Just because it's in the cloud doesn't mean you don't have to have backups. It just makes doing them harder.