I'm looking at buying a used iPhone 3GS on eBay. While I'm still considering the iPhone 4, I still like the 3GS just as much. I would buy the 8GB model in a heartbeat, but this isn't enough space for me anymore. There are quite a number of unlocked handsets on eBay - some new, some used. I was wondering - how do you re-register warranty on an iPhone purchased from eBay, so that the name is changed from the previous owner's name to the new owner? This is my only concern in regards to buying a used iPhone. Otherwise, I don't see a problem. Also... Black or White, and why? Thanks in advance!