People under 18 also aren't allowed to watch porn, and people under 21 definitely can't drink.

Fair but I was suggesting that Facebook is really only useful if you have friends but when you or your friends can't signup or their parents won't allow them to signup (in my case), there's not much reason to use Facebook.

It is kind of like not needing LinkedIn until you're in college.

There's a pretty big difference between grabbing content off some site and establishing a social media presence, surely?

No? In one case, you click a button and/or check a box to confirm you are of a certain age to see porn, in the other you enter a wrong number into a specific field during account creation.

In then end, people desire something (access to content and/or interaction), and all that prevents them from having it is being completely truthful in one spot about a question that really doesn't seem that important.

It's not very hard to lie about your age - they don't ask for any proof or verification.

My middle school aged kids have no interest in Facebook at all. Instagram definitely, and texting constantly. I'm sure Snapchat will come soon too.

From the instagram terms (http://instagram.com/about/legal/terms/) you must be at least 13 to use instagram.

I don't think that's really stopped many people. It's not that difficult to lie about your age.