I dunno...
But with Americans defining their personal identity through their consumer practices (logos n shit on their clothes) I imagine t-shirts, hats, etc. probably have just slightly more buyers than porn.
Plus, your neighbor probably isn't going to give away a t-shirt for free at his website so he can scam the fuck out of a surfer with some crappy ass trojan.
Or are you asking about promoting your site with a t-shirt?
I once found a guy wearing something like "Adult Friend Finder" on the front and "Swinger" on the back at Disney Land. It was quite a sight.
