Smallest Interchangable Lens Camera
There are basically no interchangeable lens cameras that are as small as an S100.
The body of a couple of them come close, but once the lens is added they're much bigger. As they're just junk until they have a lens attached there are no interchangeable lens cameras that small.
The smallest camera and lens combo I know of is an NEX with a 16mm 2.8, but that means you've no zoom.-- hide signature --
I went ahead and got the Canon S100 as a companion to my DSLR. After reading most of the negative reviews on Amazon, at least 3/4 of them were from a lens error that Canon later had a recall to fix. Sadly when a product has a bad batch, the negative reviews grow significantly with most people not revising their review if they get it fixed. Fingers crossed the S100 will be a good pocket camera.