Twitter is also getting DDoS'd, and they have more servers than 4chan.
Might be the Jews as well, but there's also speculation that it's the US government behind it as well as they're arresting and clamping down on the OWS protestors, trying to stop them from communicating and organizing in public. Wouldn't be surprised if Mossad is behind it all in cooperation with the US, so that the US government can keep its hands clean.