i see your point, but i assure you .rar is a very large percentage compared to the ones you've listed, and speakng as someone who does a lot of downloading, .rar is the most used format i've seen by a wide margin.

i'm just giving this info out as advice for people who might have a lot of .rar files on their pc and didnt know that symantec couldn't scan them.

and for the question of where does it stop, well, kaspersky antivirus supports over 700 compression formats, so as long as you got a good AV, it shouldn't matter what format you use.