One of the biggest differences between charitable use of cpu cycles and other forms of charity is that at present time charitable cpu cycles are not tax-deductible. Which is a shame, because if they were tax-deductible we'd see a lot more computing power devoted to whatever distributed project you could name...and no, I have no idea how one would implement such a system... Still, a large corporation that otherwise left its myriad desktops alone all night could thereby stand to benefit as much as the recipients of project data.