Foiling Google's GMail

I have a suspicion GMail creators thought of this at some point, but here is my prediction anyway:

Someone will open up a website offering a ROT-13 encryptor/decryptor as well as an internet explorer toolbar application. The application will automatically switch that e-mail you just typed up into the encrypted version, while the recipient will either paste it into a web form or use their own toolbar to auto-decrypt it.

The reason: Google's ad-words filters will not match a single word. Oops.

Lets see how long it will take for this to appear (if at all?)

Update: 8/26/2006 - Freenigma crypto browser plugin is promising to do what I described above via a Firefox and using real cryptography. Freenigma web site name was registered on 03/07/2005, which makes my prediction about 7 months ahead of that time...