This is kind of old news, since the post I'm grabbing off of Fazal Majid's blog was actually last updated a year ago, but it's interesting enough, especially since I imagine some of the Nikon cameras mentioned are still in use.
From the post:
Implicit is the assumption that the RAW file is pristine and have not been tampered with, unlike JPEGs that had post-processing such as white balance or Bayer interpolation applied to them, and certainly no lossy compression. This is why the debate can get emotional when a controversy erupts, such as whether a specific camera's RAW format is lossless or not.
The post then proceeds to look at whether Nikon (compressed & uncompressed) RAW formats are actually lossless. Interesting, especially if you shoot with Nikon.