I think extraterrestrial life must exist or it is a very large lonely universe.
I'm not sure we can even begin to imagine the benefits of finding other intelligent life. I choose to believe that there are no dangers attached to its discovery, after all if they were close enough to be a threat of any kind we would probably already be aware.
Do I think we should send out a signal? Yes leave a light in the window. I think universal values, mathematics and or known scientific data would be best to transmit, sort of an interstellar Rosetta stone.
Why do I run seti I guess like everyone else I want to get the message that ET is trying to phone home and I got the call. I think this is a very worthwhile project.