http://www.sythe.org
If you want an example of a booming forum marketplace, there's your example. They don't use an iTrader system, they use something even more outdated by having voucher threads. However, Sythe is running on a dedicated server and is literally booming in marketplace trades and whatnot.
I'm not saying TF should focus on bringing back traffic by utilizing its marketplace as a selling point (in the far away past, it used to be), but that site is a great example of how it is done.
TF should be about freelancing and what it's like to be a freelancer. Hence the name, TalkFreelance, so it should be a community for freelancers. Ultimately if you have a community of freelancers, then your marketplace here will be booming. When one falls, both will fall, at least as long as you try to remain a freelancer community.
Food for thought.