The cyber-criminal groups behind fake anti-virus (scareware/rogueware) infections have run into some significant roadblocks over the last few years, but there is much more to the overall story.
Some groups have been arrested. Some have had their operations and entire call support centers shut down.
Some groups attracted too much attention, picked off the low hanging fruit and eventually walked away from their botnets.
In some cases, the groups just weren’t very skilled at developing anti-anti-malware techniques, blackhat SEO, and malware distribution. They couldn’t keep up with the changes in anti-malware technologies, weren’t exactly dedicated to the effort, and simply fell off the map.