In late 2005, it was found that one of Sony's Digital Rights Management software could compromise a user's computer by exposing it to viruses.
[More info]
[Sources]
Read them all

I think they're actually acting against game theory. [The people at Microsoft are] doing what's not in their interest by cracking down on piracy.
Carl Howe, Senior Analyst (Software Industry), Forrester Research
[Source]
Read them all