Only Olympus and Panasonic build 4/3rds or micro 4/3rds cameras. The Sony NEX series are interchangeable lens camera systems. There are really no non-proprietary interchangeable systems. The Sony NEX uses the same APS-C sized sensor as in many larger DSLRs in the Sony family. The lenses are not generally interchangeable between the two without use of an adapter and some other caveats.
There is a class of cameras sometimes called EVILs - for Electronic Viewfinder, Interchangeable Lenses. They are also called ILC - Interchangeable Lens Cameras. Many manufacturers make models that fall into this class, but they all have different lens mounts and sensors. Panasonic and Olympus call theirs micro 4/3rds. Sony, Nikon, Pentax and Samsung also make cameras in the same class, all with different naming conventions, but none of them are 4/3rds.
It's similar to DSLR cameras; they all have different incompatible mounts and lenses, but they're all DSLRs.
I did not realize that there are more "EVILs" than just 4/3rds.
I know this is in the sony forum, but I am going to ask an addon question.
Looking at more EVILs, it does not look like the Nikon EVIL has the same mount as their SLRs. Is that true?
Absolutely not the same mount on any of the EVIL cameras to date as on their bigger siblings. This is generally due to the difference in the mount to sensor difference when you remove the mirror box. This reduction is key to allowing an overall reduction in the size of the lenses in these systems even when using the same sensor size. That said, the Nikon Series 1 system is a radical size departure from the other EVIL systems. The Nikon uses a fairly small sensor to allow for even smaller lenses than micro4/3rds. It will also put it at a big disadvantage with third party manufacturers like Sigma and Tamron. They can make lenses for APS-C sized EVILs that will likely be fairly easy to adapt to the somewhat smaller micro4/3rds sensor size. This will result in a lens that is a little large, but not too much on a micro4/3rds. On a Nikon Series 1 it would be closer to twice as big as a true Series 1 lens and overwhelm the camera.