I read somewhere that Google has changed policy and now they don't give too much important to DIRECTORY SUBMISSION AND CLASSIFIED ADS. . .
According to google changed policy Classified Ads give little bit of importants and give good ranked in the google page
Classifieds sites are more related to trade stuff (buy, sell etc) and may have no (or just little) effect on SEO.
Most classified ad sites are spammy. Legit ones are good for what they are intended for, selling something.
Classified ads is strategic positioning and gives an advantage over competitors,and helping the high-traffic on your website.
Of course , that not much important in classifieds submission in SEO Techniques, but we will get leads to our business through on classifieds sites.
Ya i agree with you classified sites are genrally used to get sales to your website and the main factor to get high PR is do regular seo
Now we need to pay more attention towards our backlinks profile after google penguin updates. Google can decrease your PR if you have more than 50% of your total backlinks with same anchor text.
based on my experience classified ads are good in promoting your site but I rarely see it as back links of my site. So, in my opinion it won't help much in the serp.
Classified ads are good and effective in promoting your sites or products.In terms of traffic point also it is important,definitely promoting the website can be done through classifieds.