Let me butt in and have a try:
SETI has:
1) one sample of intelligent life
2) nothing to suggest that it can't happen (though it may be a very long shot)
3) a number of individual "dots" connecting the non-living to simple living forms suggesting that chemistry could have connected those dots and no reason to think it can't
So a hypothosis (speculation even) is formed: There may be other advanced intelligences out there and some may be at the right stage of technological development.
To test this hypothosis one can do a number of things:
1) look for life at a primitive level where we can
2) look for environments suitable for life something like ours (planet searchs)
3) look for technological side effects (SETI).
The current searches are limited, cheap and very, very long shots but, given the pay-off, worth it.
ABE
Note that for now they are not:
Looking for exotic forms of life as posulated in SF for which we have no evidence at all or reason to suspect might exist.
Considering searching for life forms that are so utterly different and so utterly alien we might stare them in the face and not recognize them (what could be more alien than an omnipotent god ?).
They are only going where the very limited evidences suggests there is a chance (however small it may be) of success.
This message has been edited by NosyNed, 04-27-2006 01:01 PM