And the other bad guys wouldn't be able to do this? There are only 2-3 common anti-virus products it's not hard to check if you are detected by Mcaffee/Symantec/AVG
Most antivirus products simply check for signatures. That way you keep paying for updates and they sell themselves on how many 1000s of viruses they detect.
Yes you can't have perfect heuristics and some of these are operating system issues - why does browsing a USB key run a program, why can a game on my phone access to my address book, why can an app connect to the internet without me knowing.
At this point do we just give up on both antivirus AND using general computers to access the web? Should we just use settop boxes with no persistent writeable storage?