I've been reading posts on this board for a while and this one is by far one of the most balanced I've seen. I think we all need to get a grip of why we are here in the first place. Some people may prefer to have a public persona here in order to protect their privacy and perhaps even wellbeing of their families. So way even tell all the details??!!
One sure sign if people are genuine though, in my experience is if they do not go out of their way to to protest their "genuineness", "innocence", "cleverness" etc. while smearing somebody else at the same time to EVERYONE who would listen to their story. In my opinion, such people don't really need friends but ego-trophies on their wall, and while we are at it, real friends do not shy away from pointing obvious errors and ego-trophies hunters are of the sort 'either-you-agree-with-me-or-you-are-my-enemy' kinda like some president I've heard of.
So you can generally see if somebody is genuine or not by a simple test: are their post generally only about gathering people who will praise them how great, beautiful, smart, anything else, they are. I'd say such people actually need parents not friends regardless if they are 20, 30, 40 or more.