I have been using spare CPU cycles for the Seti@home project for the past 8 years and have contributed around 335,000 credits to the project (90% of these in the last year). SETI@home is also considered the largest virtual computer in the world at 1.2 petaflops which is a lot of processing grunt. We haven’t found any extraterrestrial life yet, but I think there is no harm in trying!
I have been involved in SETI and a few other distributed networking projects over the years including chess960 and the search for the largest prime number. Although all of these projects require users at home or work to donate the CPU time to the projects, I think there could be a great use for these CPU cycles to be used in the workplace to share the load of some of the more CPU intensive systems we now have. Most desktop PC’s have dual or quad core cpu’s that sit at around 5%-10% at most all day. Large graphic rendering projects have been shared out for a long time at 3d design companies, but I have never seen it done in any other type of company that I have worked at.
Grid computing like this will move from users donating their CPU’s to some sort of home processing system where people will be paid to process units of a large project for a financial company or some other large business. This brings the issue of data security to the forefront, but with encryption and users only getting small parts of a larger project, these issues can be overcome in time. There are a few businesses doing it now, but none of them on the major scale that could be harnessed from all the CPU’s in the world today.