Yes, I agree with ammoun and getjimmy on this one. Use the search function and input the user name so that you can see if someone else has posted an issue with the username in question before conducting business with them. Carefully look over their itraders and the itraders they have left for others along with their previous posts to judge what type of person you will be dealing with.
Double Mary is a smart cookie, the best way is to look through their previous posts. If you do thos, you can pick out who is on here for scamming. They will be the ones posting stupid relies to build posts and trying to do 10 cent trades to build ittrader. Just for information, the two sites linked have no connection to DP, they were started by members from the forum and are expression of their opinions.