Which raises an interesting question; if you have an E-mount camera, such as the NEX-FS100 (or the forthcoming NEX-VG20), should you buy an E-mount lens, or spend money on another lens and use a lens mount adapter?
It's an interesting question, because Sony's E-mount has a short flange focal length and because of that it's possible to use lens adapters for many other lenses with the E-mount. However, the reverse is, I believe, unlikely; it won't be possible to use an E-mount lens on your Canon, Nikon or 4/3rds camera.
On the other hand, there's a lot to like about a lens that works with your camera without an adapter, not least of which is that you don't have to deal with an extra piece of equipment. Secondly, unless you buy an A-mount lens and the Sony A to E-mount adapter, the camera can't communicate with the lens, so you're always in full manual.
So should you buy a lens that's limited to the E-mount, or would it be better to buy a lens that's useable on other cameras? As the owner of some Canon cameras and lenses, it's a question I'd have to think seriously about. Of course, it's not a real problem for me at the moment as I don't currently have an NEX camera.
 SonyAlphaRumors: A source explains why the 24mm E-mount Zeiss is so big
 As defined at Wikipedia: the flange focal length is: the distance from the mounting flange (the metal ring on the camera and the rear of the lens) to the film plane.
 Wikipedia: Sony E mount
 Birger Engineering is working on an EOS to E-mount adapter which provides lens communication, but the adapter is still not shipping.