I think it will be a good thing that accounts under the rank of Jr. Member for example can't access the forum sections - Goods - Currency exchange - Lending, and so on. Sounds quite harsh, but it may help.
I don't think limiting them from the Goods section would be a "good" idea. Sure, there are lots of Newbie members who are here to scam (it seems more often than not a Newbie is trying to scam), but there are new members here are well who are genuinely interested in purchasing or selling something. If users use escrow when dealing with Newbie members, they're covered pretty well. Currency Exchange and Lending might be something to think about though, especially the Lending section. I'm not sure I've ever seen a legitimate loan request from a Newbie member (legitimate as in having valid collateral).