Sorry, sugarmouse, but there's, as far as I know, no password security or locking device on Kindle. So, the best advice is not to leave it where other people will have free access. It's no different if you had an illustrated spanking novel in your hands. I supose that you wouldn't leave it in public place. From other side it is something to be suggested to Amazon.
Kindle, by itself changed my view on eletronic reading with its "Digital Ink" tecnology. Now I can relax near my pool sipping a caipirinha and reading a thousand books on my Kindle with sun shining directly on it. Try it with iPad or any laptop.
