To help facilitate transactions in the buy/sell forums, can the email of people registered on this forum be a requirement as part of the information? I have seen where people interested in items (including myself) ask for email (or more information) since it is not listed in the profile of the seller. If you are trying to prevent unneeded bumps due to questions asked on the forum page, this will make this much easier.
They are also causing bumps by people not responding to email sent, which could also be helped if the email was in the profile to message directly.