Fact: Microsoft is an investor in Facebook.

Fact: Bing powers Web search functionality on Facebook (and has since 2010).

Fact: Microsoft makes use of Facebook data to power its own Bing social search.

So given these facts, one might assume that Facebook also is using Bing to power its just-announced Graph search. (Graph search is different from Web search; it allows users to obtain more refined results based on information users are sharing inside of Facebook. More details on how this works .)

But is this actually the case? Is Microsoft's Bing what makes Facebook's Graph Search tick? And if not, has the Microsoft-Facebook duo gone from friends with benefits to frenemies with investments?

I asked Microsoft on January 15 whether Bing was powering Facebook Web search and received an inconclusive answer from a spokesperson. The answer, via an e-mailed statement:

"Web search and Graph search are different. The way web search works is when you do a search on Facebook, the results page features a two-column layout with Bing-powered web results appearing on the left-hand side overlaid with social information from Facebook including how many people like a given result. On the right hand side, you will see content from Facebook Pages and apps that are related to your search. In addition, Facebook’s Graph Search enables people to search across all their content and connections on Facebook to discover new people, places and things."

A new post on the Bing Community blog site also doesn't directly answer the question. From that post, authored by Derrick Connell, Corporate Vice President of Search:

"As part of this product (Facebook graph search), our two engineering teams worked together to advance a unified search experience. That means that when people want to search beyond Facebook, they see web search results from Bing with social context and additional information such as Facebook pages."

Yes, Bing is generating the Web search results. But is Bing powering Facebook's graph search? I was still not 100 percent sure after reading (and re-reading) the January 15 Bing blog post.

I tried one more time. Three was the magic number. Microsoft is not powering Facebook's graph search. From the aforementioned spokesperson:

"Confirmed that Bing only powers the web search functionality on Facebook. We do not power Facebook’s graph search."

Microsoft, for its part, is continuing its own experiments on making Bing search more social. But in order for social results to show up in Bing, one's friends need to opt into sharing information that way. As I've noted before, I don't like seeing my friends' preferences and recommendations show up when I search for something on Bing. (No offense, "friends.") So I have disabled this kind of connection between Bing and Facebook.

I like my search separate from my social. Let's see if Facebook users understand graph search enough to decide the same -- or differently.