Our small corner of the internet freaked out yesterday when Linn Nygaard noticed that all her books had been wiped from her Kindle and her Amazon account had been closed. Nygaard's account and books have since been restored but the incident has caused many to remember that, oh yeah, the Kindle is more of a Blockbuster Video-like rental store than a reading device. To that end, Zachary West has posted instructions for converting all of your DRM'd Kindle books into a non-DRM format that you can read on any number of devices.
Source:
http://kottke.org/12/10/how-to-permanently-save-and-store-your-kindle-books