Why is my "new" iPhone 4 already synced to another iTunes?

Just upgraded to a new iPhone 4.. the phone was activated at the store (however they do that).. I bring it home and plug it into my iTunes for the first time and it shows up with another person’s name and tells me its been synced to another iTunes. I can sync it to mine instead, but it still shows someone else as the owner of the phone in iTunes.. what it this all about? Was I not told the phone was used, or is this a common thing? Does it get synced to some iTunes before it ships out or when its activated at the store? My old one wasn’t like this, it showed up as new and had me set it up, name it, etc. What the hell?