Has there been some sort of falling out between Arment, Siracusa and Gruber - they all left 5by5 within a short time of the Gruber move, and in my opinion their shows are now worse.
For Gruber, I assume it was just money. Someone else offered him more or an ownership stake that he wasn't going to get from 5x5.
Siracusa and Arment both said they thought the shows had run the course. Siracusa is also a regular on The Incomparable [4].
[1]: http://5by5.tv/talkshow [2]: http://5by5.tv/hypercritical [3]: http://5by5.tv/buildanalyze [4]: http://5by5.tv/incomparable