Adverts for these things get into legitimate sites all the time through things like adwords, even though they're normally taken off quite sharpish, they're still there. They still cause problems and numpties do click on them. The old IBK error keeps appearing. As long as people aren't educated as to how this all works the problem will remain huge.
The problem with Anti-virus is that every few years a new guy appears on the block. First it was Norton, then Mcafee, then AVG, Kaspersky, and now whatever AV's the in-thing to use. There are new viruses out there all the time too, and if there's one thing that normal people are aware of it's that there are alot of viruses out there, and that your AV doesn't give 100% protection, so when something pops up saying "You're infected! Our AV will cure it!" they're likely to believe that their current AV is defective, because clearly this one spotted it, they download it and BAM! world of trouble.
It's depressing sometimes, but gladly, I've not had to remove it from any PCs in a while, whenever I do I recommend they replace their browser with Firefox and Adblock plus (Not noscript, I did that once and I got bollocked for that a bit because 'using the web was too hard as he had to press buttons every site he went on', the guy was a real pleb but nevermind) - and ABP stopped all the ads, and thus, stopped them downloading and installing that shite.
