He is citing "personal issues" as the cause. Many people are assuming it is tied to his drug and alcohol issues, but TMZ is reporting that Jon and Richie had a Mick and Keith type fallout. Who knows? Either way, I hope these guys can get back on track someday...
Richie Sambora leaves Bon Jovi tour - latimes.com
http://www.bonjovi.com/en/news/46984519868.0/richie-sambora-will-not-be-performing-on-this-upcoming#.UV2c9qKsjTr