Yes, Sony and Google have teamed up to offer 500,000 free e-books on the Sony Reader. Free is nice, and half a million is an impressive number, but lots of free and cheap e-books can wreak havoc on your database and best-seller lists--just ask Amazon.com, which found itself with Adolf Hitler's "Mein Kampf" briefly sitting atop its best-seller list for legal thrillers in the Kindle Store, experienced earlier Thursday. The Kindle Edition of "Mein Kampf" isn't free on Amazon. What's interesting is that there are actually two versions: one costs $1.58, and the other costs $1.60. Both are fairly popular,...