Searching for alien signals. It's a hobby. Aside from the basic assumption that somebody out there is sending radio signals to aliens when we haven't done it ourselves yet (I once read a Probability Zero in Analog called "The Ears Have It" in which all the civilizations gave up on SETI...because everyone was listening and nobody was talking) - the galaxy is a big place. Our chances of picking up a random signal are very slim.
What about a signal aimed at us? It would probably be a far more reasonable strategy to pick a star we think has a planet with the right kind of life and send a narrow beam signal just for them.
Which is why some people are now saying we should target SETI to aliens who already know we're here - that is, to systems that are more or less of the right type which would be in the right place to detect Earth using the common, and relatively easy transit method. This narrows the search zone down to about 2,000ths of the sky.
It seems as good an idea as any. And maybe we should start looking at those systems.
Maybe one day we'll work out the best way to call "Hi" across empty space.