I found this interesting article in InformationWeek.  You've probably had those Registry Cleaner XP pop-up ads appear on your screen.  They look like a "real" Windows system message - they pop-up and tell you a critical system error has occurred and you need their software to fix it.  Because it looks like an "official" error and recommendation, the average user can be easily duped into purchasing something that they really don't need.

Looks like we have a lawsuit out to stop this as obviously less savvy users will fall for this alarmist type trick.  To read the article go to Microsoft, Washington State Launch Legal Assault On Scareware -- Spyware -- InformationWeek

Quote from the article:

"Social engineering scams that exploit the fear and ignorance of users can work time and again with only a little tweaking and adjustment from instance to instance," said Howes. "Plus, social engineering neatly bypasses so much security software, because it effectively tricks the user into treating malicious software as a welcome guest on the PC."

What do you think?  Should this kind of devious method of selling software be stopped?  Or do you subscribe to the caveat emptor philosophy?