Sure, I can see a few ways of this happening:
1) A virus provides some additional benefit. For example, if a virus' first stage acts as a sort of installer and pulls in some additional libraries for use, at some point of public infection rate there's a pretty good chance those libraries are available to anyone targeting programming for those systems. This becomes more feasible if AV cleaned the infectious and malicious portion while leaving libraries. Imagine, every system has libpcap one it...
2) Viruses start opening previously locked down portions of the OS to achieve their goals, and developers start taking advantage of these opening to extract more value for what they provide (in fact, being somewhat malicious themselves). This is already the case to some small degree with browser exploits. Keygen utilities that install malware seem to fit this somewhat.
This all presupposes a much more computer integrated and yet less computer aware society, which is where I think we are heading. More and more items have integrated computers and operating systems, yet we are much less aware of when this is the case (of course certain groups, such HN regulars, are more likely to be a aware of these items).
Edit: Here's a sample scenario for you: You turn on your new computer and attempt to use it to watch videos on your favorite site, but it doesn't work. You try again tomorrow and it does. What happened is that between then and now, a virus has infected your system and installed a hacked divx codec and made some changes in your browser to redirect you to some specific sites often. The author gets information about your system far beyond what is normally allowed, and you get access to videos as you normally did (possibly illegally).