Really? Facebook likely is a huge target for spam, and it's not unreasonable to think there would be false positives in an effective spam killer at scale.
I used to work on the Site Integrity team at Facebook. It's really challenging to fight spam at scale. We've accidentally blocked many top domains in the past -- mistakes happen and we work to fix them as quickly as we can.
I find it strange that people are so quick to conclude censorship. Do they really think Facebook cares what some blogspot blog thinks? Facebook erroneously blocks links for a lot of reasons such as if many people report the link or if the link gets more shares than the domain usually gets.
"erroneously blocks links for a lot of reasons" is also a problem, whether it's incompetence or conspiracy.
With billions of links being shared on Facebook every day I suspect that they error on the side of caution.
Facebook has definitely been known to suppress criticism in the past, though. I've shared articles about facebook, on facebook, and they've been removed.
Censorship is whan something is blocked or removed, whatever the reason. Facebook has several years of documented use of censorship, if you remember the case of thepiratebay up to the recent "hohol" case.