I think it's actually quite an apt metaphor. Yearbooks are a collection of snapshots-in-time and the kind of trite social cache signalling of shallow observations and pseudo-intellectual "deep" insights about who's going to make what of themselves that only an immature, ignorant, inexperienced kid can make. That's exactly what Facebook is: a forum for the most trite kinds of social engagement and signalling.

...Or it's just a site to keep up with friends through messenger, events, pictures, etc?

You just have to do a bit of work to filter out the crap from your timeline (unfollow/unfriending)

What you are saying might be true, except:

There are too many idiots who go and "tag" photos with people who are not active on Facebook and help create a shadow profile.

There are too many idiots who willingly give Facebook the permission to mine their address book to triangulate the phone number + name + email address + misc. contact info of people who are not active on Facebook and help create a shadow profile.

There are too many idiots who don't think one extra second about filling up the messages they send to other people who are not on Facebook with all kinds of sensitive information and help create not just a shadow profile, but one which can be mined in ways that the idiots don't ever want to acknowledge.

Oh, and there are too many idiots who think that their "right" to use Facebook also gives them the right to send the personal information of other people to Facebook, whether or not those other people consent to such abuse of trust.

So yes, it is just another site. The smart folks who are concerned about tattling on their friends have mostly left. The remnants are mostly idiots, and damn it, I just can't find a way to stop these idiots from being so idiotic other than filling up internet comment threads with not-so-subtle hints about how these idiots are fucking up my life. Do you have any suggestions for how I can stop these idiots from acting in such an idiotic way?

You have important points, but your tone defeats your purpose. Would have liked to read this comment again without the unfunny over-usage of “idiot”.

At best, their behavior is idiotic. But short of consuming our entire vocabulary with ever-further steps of euphemism, there are few if any accurate alternative descriptions of the set of people who trust Facebook.

"Naïve", perhaps, but that excludes the vast swath of people who trust Facebook for more than a rather short duration of time.