Classified Ads Classifieds work well for people when they are in a newspaper. Unfortunately an online classified has several disadvantages going for it. Publishing a classified ad in a newspaper gets your message out to as many people as the paper prints copies for. That could mean hundreds, thousands or even millions of people depending on the newspaper. An online classified is ONE ad, and since you rarely have any idea of the traffic the hosting site has, the distribution of your ad can be extremely limited.
Classifieds tend to be generic content.
The only type of commercial site that should consider installing a classifieds would be one that is looking to build a community of people, ie, a portal. Portal content tends to be very generic, non topically specific, therefore a classifieds would fit well into that sort of site. For all the others out there, installing a classifieds would be a dilution of content. And thats something to avoid at all costs. A BBS or Bulletin Board System is a double edged blade.