The Kindle only allows the reading of Amazon DRM-protected content.
Kindles can read a variety of non-proprietary, non-DRM'ed formats. They read TXT, HTML, JPEG, and non-DRM Mobi files directly.
If you read some of the Kindle discussion groups, you'll see people complaining about "no backlighting", and then a few days/weeks later they will be lauding the fact that it has no backlighting.
As glued to the net as we all are, there's vast quantities of content that is not available online.
A revolutionary portable reader that wirelessly downloads books, newspapers, magazines and blogs to a crisp, high-resolution electronic paper display that looks and reads like real paper, even in bright sunlight.