When will they learn?
Pissing off the developers whom write mods for your software that extends functionality, enables bits you may have never considered, and allows the user of your product to do the things they need to do rather than the things you think they need to do is a great way to cause those developers to leave for greener pastures.
Those developers go to your competition, the people using your product start leaving for companies that offer the things they need (rather than the ones you think they need), and you quickly become just another Microsoft swirling the toilet bowl of fail.
Hey Google! Remember when your motto used to be "Don't Be Evil"? Why do you insist on making MS look good in comparison?