Question for discussion:
Should exchanges be allowed to harvest?
You can't stop anyone from harvesting. Each account makes it's own decision
From what i know from some poloniex mods, their contract prohibits harvesting
If poloniex is NBZMQO7ZPBYNBDUR7F75MAKA2S3DHDCIFG775N3D then they are harvesting
It's their call no one can stop them. Although I must say I wouldn't do that...
If they really do, I hope they're doing it on some separate node, not on the node they use for getting information.