the best way to be secure is to avoid online payments such paypal, etc. only real bank transactions if you'r a company or something like that.. if you sell goods and want to accept paypal payments, always ask the buyer to leave his details such as ip, etc. on your own server/shop, that way you will avoid scammers as they don't like to be exposed. dp is just a forum for them actually.
I remember when I got scammed out of $200. I guess it was my fault for trusting someone with 0 iTrader