Malicious actors also buy 'aged' accounts, so you'd need to continually monitor this reputation? Seems a hard challenge to solve for individual site owners.
It's easy and effective, aged accounts buying is rare and cumbersome, when the rest are filtered out, the "buyers" stick out like sore thumbs... then wackamole is fun.
DSBL of various sorts work (mostly) for emails.
Site owners could absolutely run a distributed realitime IP/metadata reputation system.
Malicious actors also buy 'aged' accounts, so you'd need to continually monitor this reputation? Seems a hard challenge to solve for individual site owners.
It's easy and effective, aged accounts buying is rare and cumbersome, when the rest are filtered out, the "buyers" stick out like sore thumbs... then wackamole is fun.