This could actually be pretty cool, because good luck trying to memorize a random string that's a thousand characters long.  However, if you imagine that The Man was after you, and could find the RFID with a full body scan at a checkpoint, the implant would be pretty much useless.  Same thing goes with full disk encryption with the key stored on a USB key.  At a border crossing, it could be confiscated and used to boot your device, steal your data, etc.