10 gigabit Ethernet means that 10 billion bits are transmitted every second, but I don't understand how this is physically possible (let alone 100G Ethernet). The fastest CPUs today only run at ~8GHz, but even if transmission doesn't require a CPU, it still seems problematic. 

At 10G, each bit lasts only 100 picoseconds, and in that time span, I would think that gate delays become an issue. It's not as simple as setting a line high or low for each bit, surely hundreds of transistors are required in order to output the complicated Ethernet waveform.

This seems like even more of a problem on the receiving end, since the waveform must be sampled at a very high rate, and if this uses ADCs, that introduces even more delay.