As detailed by the BBC, Blizzard's latest version of WoW installs a spyware program known as The Warden. In addition to monitoring a player's system for any known cheating or trainer software, The Warden also scans the title bars of any other running program, and is capable of retrieving email addresses or open URLs.

Obviously this is the sort of development some players or potential players won't be happy about, but there's an ironic twist to the story. Apparently, Sony's rootkit can be used to deactivate Blizzard's monitoring software.

TechReport