OK, until someone proves otherwise, I'm going to assume that Boston drummer Sib Hashian (in the center, below) is the hairiest man in rock & roll. That fro has reached its theoretical limit, and the beard isn't far behind.
In second place is terrible Canadian crooner Gino Vannelli, who probably could have claimed the prize if he'd just gone ahead and grown a beard:
Conversely, Chris Robinson of the Black Crowes is making a brave go of it, but that chest looks suspiciously pasty:
Your move, Devendra Banhart.