I've only ever seen a guy with the bearmonster hoodie at my university too. A few times, actually, but always the same guy, and I'm never wearing any of my QC shirts when I see him.
I've seen a couple of peoples at shows here wearing Dinosaur Comics tees, and the odd Diesel Sweeties shirt floating around. One girl at my U wears a VG Cats shirt.
The only webcomic tees of mine anyone has ever spotted and recognized was a Toothpaste for Dinner shirt and a Red Meat shirt, but Red Meat is syndicated in the local arts & entertainment weekly, and I don't know if it counts as a 'real' webomic. My QC and Wondermark shirts go unrecognized but people always ask where they're from. I've got the Perry Bible Fellowship 'Unicorn Power!' shirt coming in the mail soon, though... we'll see if anyone picks that out of the crowd.