Almost Lost My Kindle Books

I was reading The Atlantic Monthly on my Kindle, wireless off. Suddenly my Kindle shut itself down. After reboot I noticed all my books were gone (including the pdf files). I knew I could still download them from Amazon but I was not very happy with the inconvenience and started to question the stability of the device. Things went worse when I found I couldn't download any of the archived books. After a few tries, I gave it up and started to write an email to the Amazon tech support. Before finishing the email, I turned on my Kindle again and found all the books (including pdfs) were magically restored. (I guessed it took Kindle a while to do the file system check after crash.) What a scare!