I think that censorship ability should be a setting for users, personally. For example, a nsfw button (as steemit has), but at the site level, so content that people aren't interested in seeing, like shootings, pornography, etc. can be monitored and kept out of there feed.
It would definitely be a huge statement if they did decide to adopt steemit because, as you're saying and exactly as I'm saying above, it would create more transparency, permanency, and a lack of central authority deciding what should be censored/if anything should be censored.
So your talking like, if they built an app right? Not them actually owning Steemit?
I mean, anything is possible, but, yeah, I imagine that it would much more likely be the integration of the Steem Blockchain into the existing Facebook Platform to monetize content in a similar way to Steemit/potentially use it as a tool for buying/selling on their site. :) I think it would be a little weird if they tried to actually Buy Steemit, for a number of reasons, not the least of which is that Facebook has a much better/healthier/faster system from a technical perspective. :)
It would be sweet if Steemit just overtook Facebook! ..but as a realist, I can't imagine Facebook would let that happen. :)