When I first saw the spike it was for XKCD and Penny Arcade, I was expecting it to be internet culture related. I mean at the time XKCD was still growing in readership and to get a colossal jump was a bit weird so I was wondering about a Digg or Reddit boost, then when I noticed it was wider and into more obscure terms I wondered if it was an oddball 4chan event. However I saw it in literally every term I searched, the only ones I couldn't see it in were terms that already had huge random spikes.

So I thought I'd post it here, see if anyone else could figure it out and it looks like a few people have good suggestions - gotta love HN.