Typical Cav response. The fact is, Cav is the trailing rider. He should expect riders to move left/right and come over into what he thought was a gap. The gap of course, closed due to the fact he jumped just a second before Farrar, who was also going out to the right. Then the rider coming left also.
Rule one in cycling, don't overlap your front wheel over someone's rear wheel, or don't put yourself in a position that might lend this to occur.
Cav can only blame himself, unless he was right up next to his hip with his shoulder when Farrar came over, then not much would have happened, just a bump between the two.
Also, one could say that Cav ruined the sprint and possible stage victory for Farrrar by jumping up to the right of his rear wheel which he had to know Farrar was going to go towards the same gap to get around the rider he was trailing.
Oh well, whatever. That's racing.