Turns out charity isn't dead. Take the well-known Search for Extraterrestrial Intelligence@Home. For those of you who don't know about SETI@Home, it's a massive experiment in something called distributed computing. Anyone with a personal computer, a Net connection, and a slightly altruistic streak can download an application that allows any single computer to work in tandem with thousands of other computers to crunch reams of data, one chunk at a time. Whenever users log in (http://setiathome.ssl.berkeley.edu), they can automatically download a .25MB of radio telescope data, from Puerto Rico's Arecibo Observatory, which their computer will analyze whenever it isn't in use. The SETI application searches for patterns that might indicate an alien life form is trying to communicate with us. Very sci-fi. Also very cost-efficient, since no one's getting paid for the pooled computer power. Apparently the chance to find intelligent life on one's computer (no jokes, please!) is a powerful lure for any volunteer.

Here's how I know charity thrives. Tonight, while desperately procrastinating in preparation for writing this column, I was pacing the CNET corridors. All around I noticed flickering SETI screen savers illuminating otherwise darkened spaces, as unattended computers sifted for aliens. CNET employees, it turns out, are big-time SETI supporters. Then again, seven users in Tokelau, a territory with a population of fewer than 2000, have collectively put in more than seven years of computing time on the project. Go figure

I'm no curmudgeon. I applaud the SETI program. Let's recognize, however, that computing power is not really free. I'll discount the cost of bandwidth, since SETI@Home sends only a few minutes of data every few days. But hypothetically at least, you're putting wear and tear on your system, since the application writes data to your hard drive--a mechanical device--every minute or so. And if you're crunching numbers all night and weekends, you're certainly using extra electricity. Even according to the most conservative estimates, it costs more than a few pennies to run a computer all night. Over the course of a month, those pennies can add up to several dollars. (The debate still rages about whether you can increase a computer's longevity by keeping it permanently turned on; I come down firmly on the environmentally friendly side of saving juice.)

So you, or your company, are paying some price, however small, for your largesse. No big deal. The cause is just, even if no little green men ever materialize. Ditto for sites like Distributed.net (http://www.distributed.net), which add to the store of human knowledge by tackling complex mathematical challenges. Currently, for example, you can lend your CPU cycles to help find the "Optimal 24-mark Golomb ruler" or to crack security company RSA's 64-bit encryption key (a challenge from RSA itself, which is offering a cash prize).

There's a new group of distributed computing schemes, though, that poses a more subversive threat. I have no smoking gun proving insidious intent. But I know human nature; I've seen "Survivor." I know that everybody's got an angle. If corporate executives spot an opportunity to get something for nothing (say, donated computer power from well-meaning individuals hoping to save the world), they're gonna seize it. Already, we're seeing commercial ventures that plan to harness the enormous power of distributed CPUs to conquer everything from economic modeling to better mousetrap construction. Needless to say, these businesses hope to make money on these projects. The site Entropia.com, for instance, touts laudable goals, from fighting diseases to performing mathematical research. Who wouldn't want to "Make [their] computer part of Internet history"? Some of the projects, though, like "Researching safe product designs … to test and refine them before manufacturing even begins," smack of commercialism. And the vague assurance that "Your computer can play a crucial role in making safer medicines, transportation, appliances, clothing, toys and more!" give me pause. Will future Internet business models be built on the backs of a volunteer army of computer users? Keep your eyes open. Entropia hasn't finalized its strategy yet--and it's likely they'll do the right thing by paying their users--but if you or your company is lending computing power to a money-making venture, payment in kind is only fair. Don't be fooled by altruistic sounding pitches; read the fine print before you commit.

In fact, all the distributed computing sites will need to prove their good will before they earn ours. Popular Power (www.popularpower.com), which currently hosts only a nonprofit flu vaccination research project, has commercial ambitions as well. The business will be paying its freelance PCers, but details of the payment plan are not yet set. Same goes for The ProcessTree Network (www.processtree.com), a "for-pay distributed processing network," which asks on its site, "Isn't it time your computer started paying for itself?" Most of us would answer that question with an emphatic yes. Now let's just see if these firms are serious about ponying up a reasonable share of revenues in exchange for valuable resources.

Of course, if these sites do end up paying moolah for your MIPS, I foresee a whole new problem. Let's say you could earn real cash simply by letting your computer crank away 24/7. And what if you work for a networked company with hundreds of similarly inclined employees. It wouldn't take long before those little electricity bills became whopping electricity bills, with your company picking up the tab. Just watch. This is bound to happen. Then even enlightened businesses will start posting "No Distributing Computing" signs in the hallways and adding new regulations to the employee handbook. Could be trouble for SETI@Home, which is a shame. Those ET hunters were so much fun--and a pretty fine charity to boot.