silverpig
Lifer
Didn't I hear somewhere that they've already scanned the entire available radio spectrum several times at this point and they've found nothing? Sounds like a waste of time to me.
I believe they've scanned the entire sky in the band they think signals would be sent, but not nearly the entire radio spectrum. They also have to scan the sky, which means only intermittent observation of any particular point, which means you may miss something.
Their choice of frequency is perfectly rational to us right now. Makes sense to use it.
The big achilles heel of SETI is the receivers are sensitive enough to detect earth-like transmissions only out to some small distance, like 60 light years or so IIRC. By earth-like, I mean planetary radio and TV broadcasts. Beyond that, an alien race would have to be transmitting a very powerful signal for no other reason than to be detected.