Well I have to say I have thought of this and I am somewhat confused is it the speed of light relitive to the media or a vacuum? ie in a space ship going the speed of light then you could only move towards the back if this limmited exested as an absolute but if it is to the medium electricity on the ship would be going 180% the speed of light if you messured it from outside the ship. Plus light has diffent speeds through diffent media which even further confuses the matter.
But the thing that made me really question the whole speed of light thing was when I was taking broadcasting theroy. Here is the low down 2 fields are in your standard TV or radio single a electric and magnetic field and they oppose each other which is what keeps them going as one falls the other climbs and vice versa the problem comes when you start to do the math for very very low frequencies. Me and my freinds where board so we went into a empty class room and hung out well we started to draw stuff on the black board. I came up with the idea to calucate a waveform in the micro hertz and it came to be bigger then the earth but according to the math the reaction between the magnetic and electic waveforms will be moving faster then the speed of light but all the books said a waveform will remain in perfect balance at any length yet for that to happen something has to be moving faster then the speed of light in extream cases like that.