just give it a try: I visited none of these websites before checking, it got it right, then I opened Amazon, Twitter, ... and they were detected perfectly!
I opened twitter. And now it thinks I visited youtube for some reason :-/
This is on Firefox 8.0 on Fedora Linux. Maybe the OS has a lot to do with the success rate?
Edit: I just read through the technique now and there's no way it could depend on the OS. Anyway, this is way too inaccurate to be of any practical use.
