Facebook has taken full control of its ads from Microsoft. However, Bing will still power Web search on Facebook & will serve up search ads.
From Bing Blog post:
First, we have deepened our joint work together on web search to provide even more compelling experiences to Facebook users with Bing. As part of this expanded cooperation in search, our two companies will soon provide Facebook users with a more complete search experience by providing full access to great Bing features beyond a set of links, including richer answers combined with tools that help customers make faster, smarter decisions.
Second, we are extending our cooperation outside the US, bringing the Bing-Facebook search integration to the more than 400 million people using Facebook around the world.
Lastly, we made the mutual decision that Facebook would take over responsibility for selling display advertisements on its own site.