Thanks for all the ideas!
I've been working on major changes to the market place for some months now. Features include blocking new members from creating ads until certain parameters are met. I'm also working on ways for Pinsiders to measure other Pinsiders "trustworthiness".
The market sub-forum will be integrated with our marketplace. In other words, posting ads via the forum will no longer be possible, I want one point of entry for all classified ads. A simple checkbox option to have your ad appear on the forum is included, so not an awful lot will change if you chose to select that option.
I'm also adding features like seller feedback and "Pinside verified" members. The first being sort of an Ebay feedback system where the seller always has the option to react to any reviews. The latter is a way to have Pinside verify your identity (securely) and then getting a Pinside verified icon behind your name.
This and more coming soon, stay tuned.