90% of bad trading experiences turn into "he said, he said" shouting matches on the boards (let's face it, there are no girls here). The other 10% has someone who just disappears.
The point is, we have a trading references page. If people choose to use the advice of other traders, great. If they still receive that offer that is "too good to be true" (warning sign number one!) and choose to trade anyways, go for it.
There is no way to verify whether or not both traders are indeed "good" traders unless every card is sent to a middle-man moderator who confirms the cards were shipped. Accidents do happen, and while some people do cheat out other traders, there are times where it is a legitimate accident.
If you are uncomfortable with a trader's lack of references, request that they send first. In your case, Lurtzy, and in the case of many others here, people will agree to send first as they are building their trading references.
What's the point of GAB Traders if people don't report bad traders? You should always check out that list before trading with someone you have never traded with before, even if they claim to have references.
I'm sorry that you've been burnt in trades before, but a lot of people have. I think taking precautions is the easiest way to prevent this stuff, but even if you take every precaution in the book you can still get burnt. It's the risk of trading online and even if you check through this thread, there are all sorts of accusations so it's not like the word doesn't get out.
-wtk