Idea: Store Loyalty Cards on Your iPhone

I thought this was a neat idea, if you have an iPhone -- a blogger who, like me, had a wallet full of loyalty cards from various rewards programs, decided to declutter by scanning in his cards to an iPhoto album, which is synched up to his iPhone via iTunes. I don't have an iPhone, but I understand what he did and think it's pretty cool. He said he had no problem using it at the one place he tried (the bar code scanned fine and everything). If anyone else has tried it, I'd love to hear about specific retailers allowing/not allowing this.

I think the loyalty cards hanging off my keychain weigh more than the keys themselves. :(