Why do you run SETI@home?
I run it because I believe we are not alone (I hate saying this worn-out statement : )), I have access to tons of pcs that nobody minds letting me use (friends, family, co-workers) and basically I believe that over time, the remoteness of Seti@Home finding intelligent life will cease and we will eventually find it. Possibly more and more people will use Seti@Home since the average pc is idle more than 90% of the time...why not use all that idle power to *something* besides worthless screensavers? Hopefully in the near future there will be a radio receiver located off the Earth so we can get better signals...making everything more efficient.
Thoughts about ETI
Just the sheer odds of us being the only people in the universe is a gazillion times worse than winning the lottery. Are they ahead of us in technology? Maybe. Behind?...possibly. But there must be something else out there that satisfies the definition of "intelligent life"...such as dogs, fish, or even birds. Reading about all the new stars and planets we have found in the past 5 years is truly amazing...it just makes the odds of us being alone that more ridiculous. Think about all the planets, systems, etc. that we will find in the next 20 years!
The danger would be the possible collapse of religion. Religion, as well as government, is essentially about control..."if you believe in us, you follow these beliefs, rules, punishments, etc." No current religion believes in ETs. Having them show up one day would probably cause some chaos. In fact, the ETs themselves might agree/disprove any religious belief we currently have.
However, the benefit would be that our minds are more open. Just like proving the world isn't flat...or that the Earth is not the center of the universe.