Greg Hoglund has written a program (called Governor) to monitor the program (called Warden) that Blizzard wrote to monitor their users.

He's also written a short open letter: "Blizzard, it is within your right to attempt to make your computer game that way you wish it to be, and to attempt to catch cheaters.", he says, "But, reading the memory of other processes and windows that are not part of the World of Warcraft game client is a violation of privacy."

It's a nice, polite piece of work, and he's offering up his code and source for all to use.