[kalid]

The 99.8% includes a known test set for historic viruses from the 80s and 90s. The stuff you really care about are the new things that sweep the web (Blaster, Slammer, Code Red, etc.). AV is inherently reactive, and that .2% you miss is likely the latest stuff.

[smallblacksun]

Old (meaning a year or two) viruses are still around, and can still do a lot of damage. A large part of the reason they don't is because people run virus scanners that catch them, and stop them from spreading.

[boredguy8]

Well, I mean, patching...