I think a lot of things could be abused, and rather than ban the thread completely, I'd hope a mod could make reasoned judgement when a post crosses the line.
JB had a post pointing to a rather spectacular eBay ad for a Piper Archer - outside of the obvious aviation interest, it was the marketing technique that (ahem) caught my interest.
Maybe if we post only the eBay auction# and let the ad speak for itself...