Microsoft Corp.’s longstanding relationship with Facebook Inc. appears to be slowly winding down as the social networking giant today quietly dropped use of Bing for search.

The move, first reported by Reuters, comes following the rollout of new search functionality on Facebook Monday, a move our own David Coursey referred to as a “Google+ killer.”

“We’re not currently showing web search results in Facebook Search because we’re focused on helping people find what’s been shared with them on Facebook,” the spokesperson for Facebook said. “We continue to have a great partnership with Microsoft in lots of different areas.”

Although Facebook may continue to work with Microsoft, Bing search was the front face of a relationship dating back to 2007, when Microsoft invested $240 million in Facebook pre-IPO in return for search rights.

It was never made clear just how much traffic or brand exposure Microsoft received for its minnow search engine, but being dropped by Facebook certainly can’t assist its longstanding attempt to take on Google.

For Facebook the move is hardly surprising; Mark Zuckerberg flagged search as one of the company’s key growth initiatives in July.