i just ran across this old news article from 2002
basically these guys have piggy-backed onto kazaa a spyware app (yeah nothing new there, but wait) which can run it's own file-sharing network, automatically download new versions of itself and use spare processing power for computing whatever it likes.
quote:
The company plans to wake up the millions of computers that have installed its software in as soon as four weeks. It plans to use the machines--with their owners' permission--to host and distribute other companies' content, such as advertising or music. Alternatively, it might borrow people's unused processing power to help with other companies' complicated computing tasks.
more at http://msnbc-cnet.com.com/Stealth+P2P+network+hides+inside+Kazaa/2100-1023_3-873181.html?tag=mainstry
sounds pretty badass. just from a programming perspective it's a remarkable feat. i wonder if anything came of it??? anyone remember?