When I bought the AF100 video camera, I was introduced to the world of Micro Four-Thirds lenses. Well, sort of, because I bought an adapter to use my Canon SLR lenses, but I did score a couple of lenses for the run-and-gun situations. The point is that MFT is a standard that Panasonic and Olympus started using for their mirrorless digital cameras. They're kind of like SLR's, only smaller, because they use slightly smaller sensors, and don't have the mirror and prism that allows you to look through the lens on an SLR.
Canon, Sony and Nikon also have cameras in this realm. It's an interesting product segment, because it seems like they're targeting photography enthusiasts who like control and interchangeable lenses, but would also like something a little smaller and lighter. I totally get the appeal.
The big negative is the same one you have to deal with if you switch camera brands, that you have to buy different lenses. Canon makes an adapter to use their EOS lenses, but they can look a little silly, and the smaller sensors mean you only see a fraction of what the lens captures. It annoys the piss out of me that they all aren't using the MFT standard. The Panasonic lenses I bought for the video camera are pretty nice, and I could totally see using them on a small still camera.
I have to say though that I'm impressed to an extent with the progress of smaller point-and-shoots, some of which do offer a lot of control. I have the Canon S95 from about two years ago, and it does an OK job, even capturing raw files. My only complaint about these things is that they still tend to overexpose, and they rarely have wide enough apertures to get nice shallow depth of field, even at close range. As a friend put it to me, they're good for pictures, not photographs.
I'll be interested to see if the small mirrorless thing continues to grow in popularity. If I ever did decide to try it, I'd probably go with a Panasonic since I have a few lenses.