I created a bot that checks for some mis-typed tags. It was just for fun really, but people seem to appreciate getting told about their mistake. I restricted it so each person only gets told once, so it's not generating too much traffic.
We don't have ways to reach all users apart from via comments or transfer memos, so there could be applications where it's going to warn them of stuff they may be doing wrong or reminding them how they could be doing good. Some people just won't know much about how Hive works, so hints can be useful. Just have to get the balance right so it doesn't get annoying. I know some bots have a STOP option. It ought to be possible to opt out.