“Bluesnarfing, bluebugging and backdooring have been in the spotlight for over a year now, and, finally, the mobile phone industry have reacted and are issuing fixes for these very serious problems. Accordingly, the time has come for full disclosure..”
A good deal of really interesting material on just how open Bluetooth is. (From those fun folk at the Chaos Computer Club). Rather than discussing philosophical approaches to security, the information here is the practical demonstration of a number of security flaws (some of which are surprisingly simple).