What's the matter with a little arbitrage between friends? <a target="_blank" href="http://www.concertin.com">ConcertIn.com</a> is an interesting music discovery system that uses your Facebook social
<img src="http://www.crunchgear.com/wp-content/uploads/2010/11/ConcertIn.gif">ConcertIn, built by past <a href="http://www.concertin.com/2008/05/live-concerts-the-best-elevator-pitch-at-techcrunch-mee