It's a fine line. Last summer during the original epic Shaq/Kobe rap thread things started off strong and got derailed quick by the arrival of some horrible rapping trolls. There was a rapping V-Span, Scola, Nash, Raja Bell, Reuben Patterson, and TPark, none of which were much good. I think even Lebomb got in on the act towards the end and put the final nails in the rap coffin for a while.
Rapping MJ and Larry are pretty good additions to the rap troll line up but, as I said in that first rap thread, we're getting dangerously close to that time period a few weeks after 8 Mile came out where everyone suddenly thought they could freestyle.