Can someone give me an example of a "direct selling" social media site?

Hi,
It seems that the only way to sell using a social media site is by outwardly advertising or tweeting about whatever.

Is there such a site that allows direct selling without having to pay for the ads you place? Or, is there some other way to sell products that I'm missing?

 

You could possibly charge for being put into a database. That's how Tumblr makes it's money.