These are usually anti-spyware or security software applications that use various forms of deception and/or unethical means or show a history of negligent false positives to goad the end user to make a purchase.
In some cases these applications maybe downloaded with some form of unwanted software at which point the rogue application is offered to the customer as a way to remove the unwanted software.
This rogue anti-spyware was run on a clean machine. False detections and false positives were prevalent. It was detecting good programs such as Ultra Edit.
They are listed on Spyware Warriors rogue site: