If you were the CEO of a social network behemoth that boasted 2 billion monthly average users, would you fix it so nobody could block you and your wife? That's the claim some Facebook users directed at Mark Zuckerberg and his wife Priscilla Chan when they found the function didn't work on the pair, but the actual reason has nothing to do with ego.

It was way back at the start of the year when reports began emerging of an inability to block Zuckerberg. Doing so asks users to confirm their decision, warning that the CEO will no longer be able to start conversations or add you as a friend, which, let's face it, was pretty unlikely to happen. But the next popup simply explains that "This profile can't be blocked for now."

It was later discovered that attempting to block Zuckerberg's spouse, Priscilla Chan, is met with the same lack of success.

Rather than being some awful "my site, my rules" scenario, Facebook explained that the reason the pair can't be blocked is because too many users have already done it. Thanks to the way blocks are coded, there's a limit to how many times one person can be blocked.

"This error isn't specific to any one account. It's generated when a person has been blocked a certain large number of times. In very rare instances, a viral campaign will develop instructing lots of people to all wrongly block the same person," a Facebook spokesperson told the Guardian.

If for some reason you're determined to hide yourself from a member of Zuckerberg's family, it's still possible to block his sister, Randi. Or you could try to show the fifth-richest person in the world how much you dislike him by blocking his dog, a Puli named Beast.