Stupid and addictive, it's described by it's creator as, "a mashup of last.fm and Brucie's Play Your Cards Right. Can you guess which group is the best (ie. most popular)?"
So far it's told me that Pissed Jeans is 125 times better than Freddie Gibbs, and that ESG is 4306 times better than Dusk + Blackdown vs. Grievous Angel. True story, last fm don't lie.
Sorry if there's already been a thread on this.