AllFacebook says that Facebook has declared "war" on Google with an "Open Graph Search Engine" that'll create a semantic index of the web (via Like button) and eventually make Facebook search better than Google.
"Over the past year Facebook has seen growth in search query volumes and has started to approach AOL in terms of overall query volume share, according to comScore. AllFacebook shows that non-Facebook sites are now starting to appear and rank in "Facebook" results as opposed to "Web Results", as though they were internal Facebook pages — based on how many "Likes' they have."
The information available via Facebook search as opposed to Bing on Facebook is quite thin right now.
Google, Yahoo and Bing (proper) provide a much more coherent and complete user experience when people really need information.