@djsumdog I could've sworn that there were some sites that are using them for sign ups, not just DDoS protection, but I can't think of any on the top of my head.

@djsumdog @xianc78 if the goal is to dissuade mass unsolicited requesting, either is the same. proof of work bothers users less since they are less likely to notice wasted battery than being asked to write analpr0lyps3 through a distortion filter