This is primarily one "bot-net" all acting in unison and they are being targeted by people like me ( @clamps ) and others ( @cheetah , @antispam ) so their upvotes and comments mean very little now.
They do still increase the vote count for posts though which is why I think the botnet is still alive and active (to try and game the #hot list)
Good point, the bots do seem to be controlled in majority by the few - the new reputation system will definately assist in this regard