We see nothing happens. We self regulate because it simply isn't done by blizzard.
I do think Blizzard does something. And I think they do a lot. They're just fighting a battle against an enemy with near endless numbers. It is difficult to win such a battle.
The problem is that the bots are often compromised accounts. So you can't just delete those accounts, because they belong to people who aren't actually botting. So instead Blizzard have to simply suspend them.
That makes it difficult to take major, serious action against bots, because Blizzard are forced to investigate on a case by case basis whether it's an actual botter, or whether it's a compromised account.
So part of the problem has to be solved through account security, to prevent accounts from being stolen in the first place. Authenticators are a good step, but it's not enough. It doesn't seem as if many players actually use one :/
Beyond that, then there's some effort being made that we don't really see. It's the legal stuff. What works better than to try and remove a near endless numbers of botters, is to simply remove the botting program. Blizzard have done so in the past by suing the makers of the Glider program for example, which resulted in the fact that people couldn't use that botting program anymore. Such action pretty much stops every botter....for a while at least.
They also do the same in regards to the people who compromise other players' accounts, and who generally run the majority of the bots. The goldsellers if you will. For example, in the past Blizzard sued Peons4Hire and pretty much shut them down, and thus all their activities (gold selling, botting, advertising, etc.).
In regards to that, it also has to be said that the players are part of the problem themselves. The only reason why these goldsellers exist in the first place is because players buy their gold. If people would stop doing that, then they wouldn't have any gold to sell, and then they wouldn't have any reason to hack into people's accounts and use them for botting purposes.
So part of the solution is also to make people understand that buying gold hurts their own gameplay experience in the end. So don't do it.
And then there's probably something to be said for the game design as well. I think Blizzard makes some game design changes to combat the usefulness of botting. For example, it's not very rewarding to bot in random battlegrounds today compared to a few years ago. You can't use Honor points on as much stuff anymore. And people wonder why it's difficult to obtain gold through PvP. One reason is probably to make it less appealing to bot in PvP.
I think there's more Blizzard can do in this regard. You can still preserve the fact that PvP rewards gear and such that makes your character stronger, but without rewarding anything that can be transfered into gold. A radical suggestion would perhaps be to remove Honor points and simply reward the gear based on wins, and then remove sell value and DE option on the gear.
Either way, there's some effort being made in this regard, but with more probably being possible.
And then there's the Warden program, which is a topic in itself. But needless to say, that program is 10x more Hal2000 than it was a few years ago, which is slightly scary in itself, but good for the sake of combating bots.
Ultimately, Blizzard do do (hehe :P) a lot to combat this issue. It's just that it's very difficult to do something that really has a long lasting impact. I mean, these botters are like weed. They spread, and they keep comming back again.