Accepting a friend request on FB from a friend of a friend. Normally I only interact on fb with people I've met, or have socialised with online via forums etc, I don't just jump straight into FB because it's such a window on your life.
Anyway, I ignored my instincts because our mutual friend is truly lovely. I played "nice" and accepted her request.
Huge mistake.
She bombarded me with invitations to pages, put me into FB groups that I had no interest in (repeatedly - I left, she rejoined me, I left, she rejoined me, etc etc) and we didn't have any other interactions of any kind as she never posted a single thing, just commented on other people's posts and in a really odd way.
I unfriended her (I didn't think she'd notice as we had absolutely no contact) and received a whole host of messages about why I'd done something so awful. I just said the truth - we weren't interacting, we were strangers, I didn't like the group thing she was spamming me with and that it's just the way it was. She continued to question me, with multiple messages, etc. So I blocked her.
The creep set up a new FB account so she could message me from that! So I blocked her again so she couldn't contact me.
And yet another FB account was set up, purely so she could send multiple abusive messages, including some emotional blackmail (I'm housebound, I don't have many friends, I'm so looooooonely, you're a horrid person, I HAAAAAAAAAATE you). That account has now been deleted so I'm assuming FB has acted on my complaint.
I'm never ever accepting anyone I don't already know, ever again. Talk about being a fucking weirdo....and she was a grown adult.