I have blocked a few users who have "made an offer" which are ridiculously low. Sure, make an offer is just as it implies but these offers exceeded insulting IMO, a real example.
I was selling an almost new Technics SL-1200G, offering free shipping (heavy beast) and no PayPal for $3000 all-in. I had an offer for $1800. If someone is so lazy to make this offer I don't ever want to deal with them.
This is just my personal take on these situations, I know some of you will disagree but I don't have the patience for this "way below low low-ballers"..