When's the last time you saw a tablet or smartphone overclocked to 5GHz and beyond? The answer is "never" and it probably won't happen for a long, long time yet. On the desktop, well, that's an entirely different story. Not only are high overclocks common, but early looks at overclocking results on Intel's Haswell parts would indicate that the fun is just beginning, and you don't even need exotic cooling to participate.
An overclocker on Ocaholic.ch's forum posted screenshots that show his Intel Core i7 4770K processor running at 5005.83MHz (5GHz) on an ASRock Z87 Extreme4 motherboard. Ready for the best part? It only required 0.904V to achieve 5GHz!
It looks like he had to disable Hyper Threading to reach 5GHz, and it's not clear if it's a stable overclock or one that lasted just long enough to get a screen grab. Either way, it's pretty remarkable that he was able to get his Haswell chip to run at such a high speed with so little voltage.