The lens is the linchpin in this whole camera weight/size v. picture quality debate. A manufacturer can make the body as small they want but there's no substitute for high quality glass elements....which are, unfortunately, heavy.
Obviously the lens is important, and that cost might be a hurdle for someone looking to upgrade. In the case of the NEX-7, the only real quality glass available is the 24mm, maybe the 50mm...for now. The M9 is a rangefinder and its body size/weight (not to mention the cost) don't make it a viable option-its over 600g w/o lens, etc.
@SamC.Farrington-I guess my point is (as a former photographer for ESPN, I understand my opinion on this might be slightly skewed)...if your going to take a camera into the backcountry, take a camera that will give you results you can be proud of, i.e. make prints. If you just want to take snapshots of you standing in front of mileage markers...a. don't bother taking a camera (b/c no one really cares) or b. take a disposable camera (around 2oz and 5 bucks).
Honestly, if you NEED to have a cheap sub-4oz camera, get a GoPro. The image quality is decent, you can time-lapse, and of course take HD video...and its waterproof. Yes, yes I know, no viewfinder. But, if you were really worried about how the picture is going to turn out you would get a decent camera.
There is no reason why (again, my opinion might be a little skewed) if your willing to buy a crap camera for $200, you wouldn't invest another $160 and 3oz to get something along the lines of a Canon S100...which has picture quality that rivals all but the best DSLR's.
@GregStein-3kg Holy Crap! If you want a lightweight fully-extendable tripod check out the carbon Velbon tripods. I have the 540L, comes in just over 900g, not bad for a full rig. I agree, the viewfinder on the NEX-7 is a bit crap, but its better than nothing.
The reality is that nothing will replace a 5D Mk.III fitted with L-series glass. But the NEX-7 gets close, and the next generation will get even closer.
Its probably a good time to mention that I no longer work for ESPN and have no connection or relationship to any camera manufacturer. I'm just a bloke who cares about taking good pictures, and think others should be too.