Windows users being extorted by malicious software into handing over money is nothing new. Fake anti-virus utilities in particular are notorious for warning about non-existent threats and making a computer very difficult to use (if not impossible) until a "license" is bought in order to remove the "infection".
Extortionware on the other hand is even more sly. You can find, for example, extortionware that will scramble documents and other data on a users' hard disk drive, and will only decrypt the information if the user pays up. This kind of infection is particularly nasty, because removing the extortionware infection might not help to retrieve your original data, and who knows, maybe paying up won't either.
Even more nasty is the use of emotional blackmail to force a user to get out a credit card. Germany's Federal Criminal police office, the Bundeskriminalamt, is warning Germans about a virus doing the rounds now that accuses victims of viewing "juvenile pornography."It pops up a window on the victim's computer, and locks out access to the system. The interface is designed to look like it was prepared by the Germany's Federal Office for Information Security (BKI) and the office responsible for copyright infringement prosecution in the country.
It displays a picture of a child, and asserts that sex abuse images of the child have been viewed on the computer. It also claims that the computer has been used to download and spread pirated content, and demands that the user pay a €100 fine for the criminal acts, or else the computer will remain locked.