over clocking is simply there for one reason, to make little nerdy kids more uber to nerdy people. In reality over clocking really does not increase any kind of major performance, and it creates what is called bottle necks. Of course getting it to work properly can be done but also puts more stress on your hardware making it susceptible or more prone to hardware failure.
Its kind of like putting NOS in your car. Sure it gives that speed boost but your engine block isn't bullet proof and in the long run it will cause more damage than good.
Not to mention processors are by design already over clocked at the factory. You really only see it in the hardcore gamer part of computer users, and really no where else. You would never ever see anyone over clock their server at work.
It is something for the hobbyist overall, and though arguably it can increase some performances in computing, but overall nothing real world in my experience. The difference between 60fps and 70fps no human would really be able to tell the difference, though the elitist know it all will definitely argue the point that they can.