Nice discussion about SETI. I liken SETI it to pure exploration: lets take a look to see whats out there. Its not hypothesis-driven but I think its an important part of the scientific endeavor. The earliest naturalists collected and observed – even Darwin got started that way. The questions and hypotheses come afterwards.

Regarding “border cases”, I’m fascinated by cases of extremely rare phenomena, observed only sporadically. For example: ball lightning -is it real? if it exists, its so rare that confirmation is difficult. Basically there’s only eyewitness descriptions to go on. Yet high-altitude lightning (Sprites & Jets) were once in a similar position: pilots reported seeing them for decades and were disregarded by scientists, until a low-light camera system was flown on a U2 and recorded the phenomena.