slate breaks it down for the ebonically impaired:
"It's the latest example of a linguistic phenomenon known as amelioration, which happens when a word or phrase uses its negative association over time. Other examples include flip-flops like "bad," which can mean good, and "dope," which means great."
not really worth reading the whole thing, but that second sentence is quietly endearing.
instead of reading that, though, watch this. hot bush on bush action. scintilating.