Ever pull a charger out from the wall plug and notice its power light stay on for several seconds? The same kind of residual power remains in even the best power supplies' capacitors juicing your PC's motherboard for as long as a minute after you hit the off switch.
For serious overclockers, residual power is a real problem. If you're overclocking, you can expect to push the envelope with your BIOS settings and cause your system to crash; it's all part of the process. You turn the computer off, and, if you turn it back on before the power is gone, you may have the same bad settings in memory or you could damage sensitive components. If you have to wait an extra 30 seconds or a minute for the PSU to discharge after every crash, that's an annoying waste of time and a killer during competitions.
