I have wanted to do business with a few people on the buy/sell forum, but the lack of security scares me. Because, no offense, I don't trust a single one of you filthy bastards . But if a secure system was set up, I think it would be a really cool area to buy/sell stuff. Don't know anything about the fancy online crap damn stuff crap, but just a suggestion.
I think that would cost this site quite a bit of money. And if a sour deal goes through, talkbass may be held responsible...
It's enough that Paul provides a forum for sales, period. If I were him, I'd charge to post there (his bandwidth, he should make money). He is nice enough not to do that. If you want security, buy from a store with a return policy.
You could always use an escrow service. I'll do some research and post a blurb in the classifieds (Another reason people should take the time and read the FAQs, etc.)