You have a very narrow-minded point of view. FB can be good for many things, evidence gathering included.
As far as subpoening anything, there has to be a reason for the subpoena. You make it sound like you can just decide willy-nilly to subpoena another person's FB page.
As for those who decide to use FB being morons, of course there are many, just as there are quite a few teachers, doctors, truck drivers, lawyers, & DIS members (you get the idea...doesn't matter how you can be grouped or labeled) who are morons. Belonging to the group doesn't make someone a moron, it's how they conduct themselves as member of that group that determines whether or not they are truly moronic.
I was pretty clear about who I think the morons are. I stand by it. And of course you need a reason to subpoena the records. I have that reason every single day.
Morons.