Well, buying a bad game isn't exactly like going to the video store counter with a particularly dirty porn (I worked at a video store and that was always funny).
Like someone else pointed out, if I like a game, then I buy it, if I don't, then I don't buy it. I have a lot of "crappy" games and I never bothered with the fact that someone might be watching me buy them.
Of course... more than once I do look over to someone else and think to myself "can't believe he's buying that POS" when I go to Gamestop...