Blizzard didn't do anything until someone took it too far, which was displayng ads in game. Goodbye Carbonite.

And it is not forbidden to ask for donations either, just in game. I won't miss the "please donate" messages from Questhelper. If i want to donate, I will, but getting spammed with it won't make me do it.

The last thing WoW needs is players getting the feeling that they have to buy all kinds of extra stuff from 3rd party businesses to stay competitive.