An anonymous reader writes: Astrobiology Magazine has interviewed Frank Drake, the creator of the Drake Equation which estimates the number of intelligent civilizations in the galaxy. He notes that potential alien signals detected by automated SETI programs have a problem — with no one there to conduct immediate follow-up studies, the source of one-time signals can't be identified:
"The long Harvard search of Horowitz and Sagan observed more than thirty signals that had the earmark of an extraterrestrial signal. The SETI@Home program has observed more than a hundred such signals. Both of these programs are automated, though, so no one was there at the time to do immediate follow-up observations. Researchers later tried to detect these signals, but, as with the Wow signal, they've been unsuccessful. So the origin of these signals is an open question. Project Phoenix of the SETI Institute also has found many good candidates, but that program could immediately determine the origin of the signal and all of them turned out to be of human origin. It may be that all the potential signals detected so far were generated by humans."