http://technology.newscientist.com/article...ware-fixes.html
Sounds like a recipe for disaster, if you ask me. 
Quote from a comment posted in response to the article:
QUOTE
This article seems to promote the concept of a "good" computer virus. The general consensus for the past twenty years in computer science and specifically information security has been has been that is an oxymoron. This article is misleading because it does not and the powerful classic counters to any argument for a "good" virus. Crackpots have been promoting these for a long time, and it seems just becuase microsoft is talking about it, it must be valid.
More on the subject here:
http://www.cknow.com/vtutor/AreThereGoodViruses.html