This may have something to do with Kimbo being friends with Seth. They've been photographed together a few times before the fight and Kimbo only fought him the first time because of the large raise EliteXC gave him, plus it was last second to find him an opponent. Might be more than Kimbo being scared...
Doesn't matter anyway as EliteXC threw in the towl yesterday. They are done as a company after losing 60+ million in a year starting the company up. With EliteXC gone it's unlikely that many other companies will be tripping themselves to sign Kimbo.