I've bought and sold to/from multiple members on here. Each transaction has went smoothly.
Ripping someone off on a site like this would most likely cause you a world of trouble. After all, the Internet is a wealth of information in many ways, and finding someones personal information from their home address, to their job history, criminal history, SSN, and relatives is quite easy with certain resources.
Here is a couple very good examples of what can happen..
Most Recent (the last few pages is where it gets good)
The epic Charlie Wenzel case..