At last — a file-sharing music chart

I was asked to write a piece recently about the agreement between the BBC and UK record companies that will allow the Beeb to publish a top-20 legal downloads chart from September. I wondered then what the difference would be between the legal download chart and the most popular tracks being shared on P2P networks, but didn’t know if anyone was doing that kind of monitoring. Well, it seems that at least one company is. Interesting technical challenge that. Wonder how they do it.