You shouldn't be surprised. It makes it a whole lot easier to implement a whitelist for news sources (e.g. the current mainstream group hurt by blogs) without having to deal with the cognitive dissonance caused by personalization conflicts.

For example, suppose my preferences indicate that I think WaPo is basically a marketing outlet for Amazon at this point. If the powers that be tell Facebook that WaPo produces "Real News", then it's harder for Facebook to show me "Real News" if my preferences say that I think they're full of it.