Any comment on the nature of what looks like a very large recent traffic spike (at least, per Alexa's graph)? What's being watched, who's watching it, any triggering events?
Just so you don't get the idea I'm picking on Alexa, estimating this stuff is hard (or the people doing it are incompetent, but that seems unlikely with so many entrants). Quantcast and Compete.com are even worse, and ComScore is expensive but no better than Alexa.