Apparently, this is because the account belongs to both have often been blocked by other users, so that no longer work when blocked.
If a Facebook user blocks Zuck's and Priscilla's profile, Facebook will provide "Block Error" information. That is, there was a problem with blocking Zuckerberg and his wife's account. Facebook also asks the user to re-block.
Unfortunately, blocking still can not be done, because Facebook has stopped all blocking efforts against both. The company insists, Zuckerberg and his wife did not get preferential treatment from Facebook.
"This does not apply to one account (owned by Zuck or Priscilla) only, but this is common when someone's account has been blocked too often by other users," a Facebook spokeswoman said.
He also said, "The purpose of this system (to refuse blocking) is to protect the owner of an account that is often blocked." We are constantly working to improve our system, especially in this regard. "
Just to note, Zuck's Facebook account is often blocked by Facebook users around the world. Apparently this happens because Zuck tends to often upload a lot of things to his account, including personal terms, statements, or the latest service up.
Thanks to an algorithm on Facebook, if there is a friend sharing Zuck's uploads, all friends can see the upload. That is, anyone can see Zuck uploaded on their feeds and not a few who feel disturbed, then it actually blocked the founder of Facebook.