Why do you run SETI@home?
One of the first things that piqued my interest was the idea of distributed computing. The concept of building a virtual "super computer" out of PCs from all around the world -- and using it to do non-trivial work -- appealed to me. The fact that SETI@home also focused on an issue I find compelling was just icing on the cake. The nature of the project got me to join. The content of the project got me to install in on every machine I could get access -- and permission -- to tinker with.
Thoughts about ETI
I can't help but believe that, even left to the mechanics of random chance, the enormity of the universe virtually gaurantees that we are not alone. But I'm also sobered by the same enormity and the very real possibility that we may never come in contact with any other sentient life form.
The laws of physics as we understand them make communications and travel over interstellar -- nevermind intergalatic -- distances problematic. As much as I'd like to ponder the possibility of a "shortcut" technology, "warp drive" and "star gates," if you will, they remain pure speculation. So, even if we're not alone, there's every chance that we will never have the opportunity to meet our neighbors or even to know for sure that they're out there. But I can't imagine a more world changing revelation than to someday discover just that they exist.
Many people have stated how slim our chances are of finding an intelligent signal from another civilization. However small the chance may be, it is at least larger than if we didn't bother to try.