Yes, people will be allowed more than one ad at a time as long as it doesn't become obtrusive. A few ads that get a few posts and eventually drop off the list would not be considered obtrusive. Several ads with long lists of items that are constantly receiving new posts and that may be relisted for weeks or months would be considered obtrusive.

If it appears that one individual is taking over the forum with classified ads that would be considered obtrusive, and in the past we've asked people with a lot of things to sell over a long period of time to become forum sponsors, rather than using the classifieds, which are mainly set up for occasional sellers.