Depends on if they are 'creatively' cropping or just hacking up the image as if they have no clue.
To 'lure' one in using good taste is one thing, but to hack out just an eyeball because one thinks they are being 'cute like the rest'....well, that 'eyeball', unless something wickedly cool is about it, certainly would not 'lure' me in and if it does 'lure' someone in and there isn't some wickedly cool image behind it, say nothing more then another rendered Vicky or Sydny face like all the rest, then I guess the person who got 'lured' in should be mad...at them selves for being so foolish, or just plain nosey that they just had to see what was behind such an uninteresting thumb.

Now myself, I crop for nudity and I crop for creativity and I crop simply because a 1024x768 image doesn't shrink down to 200x200 proper or if I do 'square' it out then the thumb looks too amaturish...therefore I get 'Creative' with it.

Depending on what I want to tease, I might pick the face of a book with a title "How To Seduce A Dragon" from within the scene and make that my thumb...good tease for a nude Vicky with an embarassed dragon now don't ya think?
Or for a huge family portrait of several characters I'll zoom in on just one of the more interesting or alureing faces and make that my thumb and then the title will tell a little more about it as well in hopes to 'lure in the suckers'. Or I might choose just a hint of the character, like a shoulder or a hand and focus more on capturing some of the background scene to give a 'feel' to the image as a whole and just a hint of the main attraction...and again, choose a title that also goes along.

Other then that, if I enter a gallery and only see an Eyeball or an uninteresting ?? that tells me nothing of the image and the title doesn't even appeal....I aint no cat and I'm about an courious as a door nail...

(P.S. don't go seeking my gallery here, I took it down more then a year ago...)