This is such an interesting thought...That (according to BusinessInsider) Facebook and Yahoo are now talking a Search Partnership. - A move that could go a long way to seeing Facebook rival Google, as No1!
......."The two Internet giants have already collaborated together on a number of small projects - - for example, to 'share' Yahoo! News on Facebook, and have recently agreed to settle a number of long-standing lawsuits over patents. ......However, board members expect the talks to lead to more substantial collaboration based around, web-based search."
Such a move could only help advance that ultimate (for advertisers) with any intersection of search and display. tiny.cc/1g5ynw
Whereby (and similar to Google's newer pay-to-play PLAs), a search conducted by any of it's 1 billion users on Facebook - could get to see advertisers within any future RT (real-time) 'search intent' marketplace, then targeting users in a much-like fashion as to Google's search results (SERPs) and Microsoft/Yahoo's Keyword based ads - as are shown within that above (pay-to-play PLAs), link.
It's still very much 'early days' - but the above 'scenario' (through an independent RT 'search intent' based marketplace) can become a reality. And its a possible situation where even Google's own advertisers can get to appear within Facebook user's search results!
But like Katherine Rushton's thoughts (swanson1) this too, is only an opinion.
Disclosure: Long LOOK