Hi @paulag, @mack-bot is operated by patrice and related to steemcleaners. It is used to flag spammers, among them a few of our "common friends" that we were looking at a few months back. Patrice mentioned on discord in early January that there are around 17k accounts on @mack-bot's flag list.
17K accounts -thats nuts, but a sign of how much work patrice has done