What I'd like to know is which one of them is fastest, if you have a really considerable set of data. Say, >100 000 images. I've tried quite a few, and most of them get ass numbingly slow, when you put them to a task like that.
On a related note, there's at least one program that works pretty much like TinEye - and predates it by several years. It had some serious issues last time I tried it, I don't think it's very Vista/7-compatible.
It's really nice toy to have. Not the fastest thing ever, so you'll need to clean all actual byte-to-byte identicals first.
But still, let's assume I really liek
this pic of Hwang Mi Hee (which I do). I don't need six different sized copies, some that might have been compressed more than others, nor some that have watermarks while some do not. I'd prefer to have just one; the best one.

Sadly I don't remember what the hell that thing was called. But if someone finds it - even better, if someone finds more than one of those, please post.

(yeah, Picasa's face recognition does something similar, but it's not really meant for this purpose)