I know some guys who are running more than 2,000 bots. They usually use packet bots which enables only one computer to run thousands bots simultaneously. Everyday they pick up hundreds of mpds(poison damage small charms used as currency) and hundreds of godly items. They even do craft or cubing automatically and produce nice crafted or cubed items very easily.
The problem they cause is that they do harm most of normal users. Normal users can never keep up with their productivity and this means unique items are not any more "Unique" but cheap garbages. They do not only reduce game's fun and interest remarkably but also cause severe burden on Bnet Server.(Think hundreds of thousands Bots!)
The worse thing is they use bots to suck normal users' blood. They are the strongest market powers in D2 item market thanks to their enormous productivity. That is to say, normal users are like their slaves who offer tributes for them. Then, what is the role of Blizzard? Blizzard is now like an ACCESSORY to help bot cheaters, to help them make real money, to help them steal time,money and fun from normal users.
I think If Blizzard has a "WIll to ban Bots", Blizzard can do it.
Now it is high time to ban bots and ban CD-keys of those who use Thrid Party programs to defile DIABLO.