This post on /. was worthy of repeating here. It’s in response to a review of a book on UFO’s:

For as long as man has realized that there are boundaries he can see, but can not effectively explore, his imagination has run amok and placed all manner of fanciful creations into them. “dragons be here” can be found on unexplored maritime areas on old maps, yeti signs are found in impassible mountain ranges, and sirens in the ocean depths.

This doesn’t mean that there aren’t monsters in these areas, mind you, but rather than man’s propensity to create them in his mind usually results in more monsters than actually exist. The unexplored regions of space today are no different than the middle of the atlantic 400 years ago.