I should have been clearer with my post:
Rock music with a rapper has been utterly gross in my opinion. Rap-styled music with an occasional rock-edge does work and I do kinda dig it. In summary:
Mos Def rocking=ok
Beastie Boys rocking=ok
Limp Bizkit rapping=not ok
311 rapping=not ok
Kottonmouth Kings=epic failure
Get the picture?