I think this is the easiest way, not sure why it's so far down on the list. Usually this is enough to prevent casual abuse. If phone number is too troublesome j

I think this is the easiest way, not sure why it's so far down on the list. Usually this is enough to prevent casual abuse. If phone number is too troublesome just use Gmail or something, they do a decent job of preventing multiply email registration. I guess the main problem is the bad actors who are determined to misuse your service will still find a way, but then you can just ip block manually