I suppose if you're trying to avoid someone who is genuinely toxic it's a way to make sure they can't contact you. A lot of the time it seems like little more than kindergarten tactics used by supposedly responsible adults.
I'd offer a couple of examples to show some contrast:
1. A guy I loosely knew from another Christian message board. He and I were friends on Facebook. Then I got a message from him saying he noticed we weren't friends any more, he didn't remember deleting me but might have done it by accident and wondered if I'd deleted him - if so he'd respect my decision but if not he wondered if I was still open to being friends on Facebook. I said that if I had deleted him it wasn't intentional, and we reconnected.
2. An old college friend of my wife's. My wife apparently deleted her from her friends list and some months later got a very agitated message asking why she had been deleted, insisting she deserved an explanation (she and my wife had had virtually no contact for years, except when this person wanted something) and before my wife even had chance to respond to the message she had been blocked.
No prizes for spotting the less mature user.
