Why so much hate for AVG? I've always found it to be very good and I think it's the most popular free anti virus.
"it's the most popular free anti virus"
This speaks for itself. If you're out there, coding viruses, and you want it to get past as many people's Antiviruses, you want to code for the most popular ones. So instantly, we know what ones we need to get past first in order for our Virus to be effective. First, you want to target consumer AV like Norton, and other paid, but weak AV systems, as most people think that what comes with their computer is enough to stop anything. Then you want to target free things, like AVG, Avast, and stuff like that, which are free, but shows that the users at least took the time to uninstall their original AV that came with their computer. Next we'd want to code for it to be undetected by things such as the paid version of Avast, Kapersky, and other ones, that get daily updates and have double/triple digit license costs. Finally, you end up with Enterprise level software, like ESET, where licenses can cost up to 300$
Basically, in the end it means that you want to code your virus to hit the most things, without spending a lot of money on testing it out.
Or at least, that's how I see it. I've worked on numerous computers at my previous job, and the only ones that were ever clean, were the ones we used on a daily basis in our shop. The ones that came in, could easily be hit by anything, because they usually ran the AV that came with the PC, or they had some "amazing free antivirus".