If you want to expand upon your classifieds section in the social arena, do what Craigslist doesn't do..add a social share button. This will give your readers more incentive to show their friends your ads.
The social button can be displayed within your ad 'info' area. see below:

I'm not posing for the glam..I was signed in. Just sayin'.
To read how to add social capacity to your ads, go here.
