FB can and does delete SL ava accounts. Last year I made one for this ava, as all of my friends from here were there and talked me into making one too. I used my RL birthday, and RL last name even as I don't have a last name in SL. Within a few months I got a message saying my account had been put on hold for being a fictional character, and that I needed to send in verification that I was real. I instead made a different account, which within weeks had the same thing happen. Quite a few of my friends had their accounts suspended as well. We had been having problems with an individual in SL and thought perhaps she'd reported our accounts out of spite, but never knew for sure, and didn't bother trying for a third account.
just to add in, none of us are in to any kind of freakyness that you mentioned, no xxx pics posted or dirty talk anywhere, the deletings were completely out of the blue and unexpected.