http://www.ascensionearth2012.org/2013/01/do-you-know-this-person-outside-of.html
http://www.thatsnonsense.com/view.php?id=1517

For those who use Facebook, when you accept or decline a friend invite, it asks you if you know this person outside of Facebook. Well... from now on, if the person doesn't look like a spammer or suspicious, I would recommend that you click yes anyway, in case it happens to be one of your fellow Omnimaga/Cemetech/TI-Planet/etc friend. Otherwise, if you click no and someone else who got a friend request from him does the same thing, he apparently gets suspended after those 2 strikes!

This was done to prevent spamming, but I do know that some people might misread the question as asking them if they know the person outside the Internets or they might be unsure if it's someone from the forums here or not, and it might be a legit person, such as a friend of your former friend who happened to see you years ago or whatever. I doubt you would want a fellow acquaintance to get banned from Facebook, even temporarily, so you might want to be careful in the future (and yes I know there can be misclicks too). >.<

Also I don't know if this is true, but my mom reported it from someone else as well. This appears to have been around for a long while too, but I didn't know until now.

From 7 to 30 days apparently, after 2 strikes (basically it takes 2 ppl clicking No and you're done). And if this happens a few more times, you're banned forever.

That's a really crummy system. I'm surprised they haven't had a lot of complaints about it.

Or to put it differently: stop friending everyone you see, it could be dangerous.

Honestly, I decline requests, but I thought that the knowing outside thingy was so they can't bother me.

They're sending a clear message: Use Google+ for people you don't know in person.