I think its a bit too easy to accidentally block someone...
You just click and you block someone... and the button is right next to the pm button...
Why is there there is no 'are you sure you want to block' to prevent possible miss clicks!?
Normally it would not concern me that someone has block me per say but for this particular user it was confused my to no end that this particular user has.... if this user has blocked me... all evidence says yes so far...