I don't know, I get some strange stuff in my inbox. Yet I like to think that when the aliens do make contact it will be with a message of peace and goodwill, not to let me know about exciting multi-level marketing opportunities. I've been waiting for the ETs, though, or at least my computer has. SETI patiently listens to sound from space, waiting for a pattern or similar sign that we may not be alone. The application is small and designed to use very little of your computer's resources.
Many people run it as a screensaver.
Some people participate because they hope their computer will be the one to pick up a non-earthly communication. Others do it for their team. The teams pool their hours together and compete against other teams for the glory of being the first to hear Radio Andromeda, or at least the group trying hardest to be so. I used to be terribly impressed with the number of UFOs I had seen, until they became plain old FOs, identified as satellites. Watching for satellites is still good fun.