Cool, ain't science brilliant! The speed limit's still there, but it can go slower if the pulses are different. Thanks for the link.
i read today that this entire experiment started by two guys having a beer and deciding that it would be cool if they could show c(vacuum) was a limit, not a constant. 2 years later they demonstrated it. pretty cool!
also - re xkcd book. It's my current toilet reader. Excellent value for money!