Yes particle, this is something I have noticed is very true in very real world situations.
Havent you ever noticed mechanical break down of your own hard drives? Ever find them to whine or perhaps whirr or grind as time wears on? You cannot possibly refute that a hard drive does wear out over time, and that reformats no longer bring back the freshness that the drive once had when it was new (for an old drive).
In the extreme example, take a "head crash" as case in point, in which the head literally hits the platters. I have found most older disks, one which were regularly used and ever abused, to be more prone to a head crash. The hard drive I am replacing tomarrow is beginning to experience these problems, as I can hear the sharp and painful scream of the drive every once in awhileas it accidentally scrapes the platters.
Here's another. What happens when you have a fan moving at high rpm for many years? It breaks down. It becomes louder over time, finally breaking down to a slow, loud crunching whirr in the end. Today's average hard drive rotates at 7200rpm. Now, a fan and a hard drive are two very different devices, but what they do have in common are bearings, which allow for such rotation. These wear out, become loud, and go beyond the point of usefulness.
Now, I am unsure of what points of my arguments you do not agree with, as you havent really been specific. Tell me what is wrong with my logic, because I can guarantee you that in my real world experiences a hard drive replacement was NECESSARY to make the machine useful again.
*edit*
Since I'm all up on Green Tea, Chai Tea, and passion flower extract, I have gone even further to push my point. Heres a video (mostly just the sound) of my old faithful hard drive that gave me years of service before I finally retired it. Over time, read/write times increased, even after formats. The whirring noises increased, and finally the head began to smack the platters. That was the day I bought a 30gig 7200rpm hard drive, which I used for 3 years until it began to whirr and read/write times did not seem as they once were.
Whoah, too long of a desc. Heres the video:
http://media.putfile.com/Hard-Drive-Spinning-Noise*edit again -- listen closely, you'll hear the light crashing*
So that 30gig was replaced with two 80gig hitachi's, which will be replaced someday down the line as they begin to show their age.