Maybe he's lost his passion for the game?
Since leaving the Bobcats he's played for 3 different teams in a short span. I think he was excited about playing in New York, and then he was traded and traded again. I remember reading before about the state of shock and pain players feel when they get traded. We all know Gerald Wallace was stunned. Maybe getting traded twice affected Felton similarly. All of this is completely speculative obviously.
I'll always respect him because he always played hard and showed leadership while in Charlotte. Shame he's overweight and unproductive now.