Firstly if you work with CPA networks you must avoid the ad classified, second the ads classified are preferable if you are an affliate par exemple in clickbank or CJ or... By the way The top ad classified site is craigslist.
Classified advertising is a form of advertising which is particularly common in newspapers, online and other periodicals which may be sold or distributed free of charge. Advertisements in a newspaper are typically short, as they are charged for by the line, and one newspaper column wide.
Usually, the need of the classifieds ads will vary from websites, products or services. So, before going for this technique, it will be recommended to know its merits and demerits to avoid the upcoming issues.
Classifieds, don't much help in SEO except placing our website URL. There are B2B portals, which may help.Also, in B2B, we can place our company's profile like description,products,services, images, keywords related to our company's website
Honestly speaking, Classified Ads in today's SEO might not have a big impact in SEO. Try something modern techniques related to classified ads like online directory listings. But classified ads can help you to increase traffic and have backlinks a little bit.
They have certain worth, but using free classifieds for SEO has to be done carefully. You must promote yourself aggressively if you wish to see any sales and subsequent profits. Paid classifieds do bring traffic but what if your funds have dried up and you cannot pay for your advertising... Then free classified ads are a very important tool in the online marketing business. They do not cost anything and can start providing results from the very moment that they get posted online.