As RFID technology increasingly finds its way into various identification documents, credit cards, and such you will see a growing market for shielded wallets and other enclosures to protect from skimming. Skimming, cloning, and even the introduction of viruses (yes, it has been done) are just some of the potential vulnerabilities to RFIDs.
Also, in some countries you need to leave your passport with the hotel you are staying at.
In such cases the passport can be exposed for long periods of time.
You need to require all people that hold your passport to insert themselves into faraday cages.