I really enjoy the feature to be able to browse by camera... have you considered the same idea for browsing by lens?
Even a combo of the two would be cool to give me an idea, for example, what a Rokinon 8mm f3.5 Fisheye CS lens can produce shooting on a 1.5x crop factor Nikon D90.
What Jase said - the exif info only contains info about the camera itself and the settings used (although it does include the aperture and focal length so you can often extrapolate from that which lens the person might have used).
@pocketmouse - My EXIF data contains a field called 'lens ID' which pulls the specific make and model of the lens that I used. It will even pull in 3rd party lenses. That said, the Rokinon lenses are not CPU lenses, and none of that information will be transferred to the camera.
Cameron - best bet dude is start a thread asking for people to add pictures and add lens info but make the point to say you're interested in a wide range of lenses else you'll just get the same 18-55 kit over and over.
Oh, and fisheye stuff always looks crap anyway ;)