Instead of buying a search keyword like they do with Google Adwords, advertisers like Lawyer.com can pay Outbrain and Virurl to act as distributors for their messages. They supply the message in the form of a link to a piece of content — a picture, a story or a video. Outbrain and Virurl then spray the link across the web via third party publishers and on social media sites like Tumblr and Twitter.
Just came across the idea for WPC except that writers form a guild or co-op instead of paying others. http://writer-publisher-curator.com