I find them irritating, in the same way that I find all the "give this to your friend" or "buy this for your friend" virtual things irritating. I dislike stuff, can't imagine paying real money for a picture of a token, and can't really see the appeal of even paying fake money for a token. I have to admit though that while irritation's my usual emotion, the one time I received a notification that "Friend X just bought you for $950!" was... just icky.