Earlier quoted context omitted.
Problem is that you cannot have both via current (from 2011+ on) Intel route: high clock speed on the CPU(achieved by OC) AND ECC. You want ECC you have to get Xeons. You want OC you have to get regular mainstream K chips or enthusiast -E chips without ECC support. I think the last chipset which let you OC Xeons and still use ECC was X58 on 1366 socket. Disclaimer: I am not counting tiny BCLK OC available on Xeons.
Because ECC and OC are targeted at different audiences. If you want both... you don't understand one or the other. ECC is to guarantee system stability. Solving rare event that become regular once you have hundreds of boxes running. OC INCREASES system instability. You put more power into a chip, increasing the probability of incorrect or malformed answers. Now both these scenarios are rare, especially for single box…
You're also not guaranteed perfect operation inside the CPU without an overclock, so if it's idiotic to combine OC and ECC, it's idiotic to use ECC at all.