Actually, I bought my last two BB's off of this site.
I figure I trusted most people here more than eBay. Sure eBay has the score of the number of transactions and feedback, but I used the amount of posts that a user had as well the type of information that the user was posting to make a judgment on weather I felt they were trustworthy. Fortunately both of them took paypal so the transaction as as easy as it was on eBay.
It's all a judgment call when it comes to buying used stuff, choose wisely.