I had a man who was obviously up to no good. He had a registered address on his account less than 20 minutes away from where I lived, yet needed my room and was sending *frantic* messages about needing the room for a same day rental. When I declined, he started sending very rude messages, but not really crossing the line into threats. I am suspicious of local accounts to begin with, and in this case I am certain he wanted to get into the room for some hidden purpose. I was able to stop the message by sending a report that he was being offensive and then asking in the report he be blocked (the block button is, as many have said, now permanently gone).
Coincidentally, I just had another incident recently with a woman who told me flat out she only gives 4 star reviews and will never rate my room as a 5 star. That obviously I can't have, since 4 star reviews are actually bad and can seriously hurt a host. I am going to select "not recommended" on her latest stay and will see if she is able to re-book. I think the system at last has it where if you don't recommend someone, they can't stay with you again.