If the icon is stretched or weird or blurry or has a baby in it or animates among several completely different photos, I'm out.

Yup, first impressions really ARE everything. Exactly. I don't think it's cruel to think that, it's human instinct, actually. It's the same me knowing that I should probably avoid that creepy looking guy sitting in the corner of a pub. And generally (even though not always) your first assumption is correct. Something's OFF and your brain is telling you that it DOES NOT WANT.