Three different eBay sellers have all sold me USB Bluetooth adapters (at costs varying from very-cheap to brand-name-premium) with duplicate addresses*. I'm currently waiting for the third one to stop ignoring the law (and me) so that I can return the most recent purchase.
I was ready to give up and decide it was now impossible to buy genuine Bluetooth devices that comply with the Bluetooth Specification when I tried purchasing some Belkin adapters from Amazon, and it turns out that despite the increased cost these actually have unique addresses.
* Bluetooth adapters with duplicate addresses means that if you
happen to be using your adapter within range of someone else who got
theirs from the same manufacturer's batch, you'll get conflicts
accessing devices because there will be two devices on the network with
the same address. Avoid Dynamode and cheap unbranded devices.