Wikipedia writers have a sense of humor! Sort of. A few users are posting stickers that read "citation needed" — a footnote attached to dubious claims on the collaborative encyclopedia — on real-world ads. It's a more flexible joke than putting "Hammertime" stickers on stop signs. It's also less funny than Stephen Colbert getting banned from the site, but cut the nerds some slack. If we learned anything from LOLcats, it's that nerd humor becomes mainstream humor.

Photo by Bekathwia on Flickr