i have a 2 year contract with AT&T until march of 2010, and i have no need to get the iPhone 3g. however my little sister wants to get a 3g iPhone. i'm wondering if there is an advantage to adding her to my plan, or if she should just get her own plan? no worries here about credit or anything like that, both single as well, so whatever would be the smartest we're gonna do. any advice is appreciated.