Accounts that have large or many delegations can be suspect as a first filter to look into. Then, transactions can be looked at to see if they receive transfers often and upvote same people who send the transfers. This would identify a vast majority of bots. Checking for refunds/returns is also a cross validation. All it takes is some activity to catch a bidbot account.

Changing the default front page is something that should have been done a year ago... :/