Until someone gets a Kindle and some downloaded DRM-ridden .AZW files I don't think we can know for sure, but I assume .AZW is identical to .MOBI. However, MOBI DRM is PID-based and the PID is presumably not easily available on the Kindle (since the Amazon servers already have the PID). Without the PID it won't be possible to make secure MOBI files for the Kindle.
One thing to check will be bytes 61-68 of the file. If this is BOOKMOBI, then this is evidence (although not definitive) that the file is using the standard MobiPocket format.
Edit: The DRM-free KindleUsersGuide.azw is a BOOKMOBI file.
Last edited by wallcraft; 11-19-2007 at 10:32 PM.