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.
A rogue anti-spyware application which displays false positives in order to goad the user into registering.
Huge amount of false detections
Not allowing the user to watch entire Location
Forcing the user to register the product by showing regorous warning messages
They seem to have hacked the site wunderground.com. When you click http://www.wunderground.com/global/stations/08181.html?bannertypeclick=miniWeather2 (apparently only the three or four first times you do running) they resend you to http://hotest-tgp-pics.com/?id=voodsky.