It may not have happened to YOU, but it's pretty bold to discount that it's happened to anyone based on your personal experience. If you have the evidence to back it up, it might be different.
Myself and others have experienced hard drive corruption as a result of an unstable overclock. Instability means incorrect calculations and flawed memory reads, which results in corrupted data. That data is then written to the hard drive, causing corruption in everything from the registry to filenames, programs, etc. It happens, trust me. It may not have happened to you because your overclock is stable.