I, for one, am glad that Pandora sends at least the gender to the ad servers... it's a little disconcerting to get on Pandora with my wife signed in and see tampon ads.
I do end up with 'interesting' coupons every so often. It's a little like hearing back from an estranged friend.
Or, alternatively, some other social signal that people wanted to trade, similar to Button Men at conventions: http://en.wikipedia.org/wiki/Button_Men