This team-up will help both companies increase ad revenue for their respective ad platforms especially Facebook's FBX. This platform known as Facebook Exchange launched in June 2012. The focus here is for advertisers to sell ads through Facebook that stick. This means users are essentially followed by these ads as they visit other sites.
Google's DoubleClick Bid Manager is the search engine's own marketing tool which will purchase ads on FBX. It makes perfect sense for these companies to work together. Both have a huge audience to reach out in order to generate this revenue. Of course, the tech industry is very competitive so these partnerships occur so rarely. It's unknown when these companies will start this new deal.