They are a scam. I've been scammed as well.

Along with the above thread, I have made a scam report here:
http://www.reddit.com/r/Bitcoin/comments/261r1t/scam_alert/

Details of the scam are in the comments. Basically, they make 1 or 2 successful trades and then take your bitcoins on the 3rd or 4th go around. All I have to say is thank god they did it this time or I would have sent 4 or 5 bitcoins next time! The thought just makes me shiver...

TL;DR
They SCAM you. DO NOT USE