A little understanding goes a long way
First and foremost, I think geek squad is filled with idiots that refuse to make it any farther in their career than they already have.
Second, I myself have no college education, and was somewhat formally educated in the military. Instead I have 8 years of enterprise-level experience, an A+, N+, Sec+, MCSE (upgraded to MCITP), CISSP, CEH, CCNP, CCDP, and am a lab exam away from a CCIE. None of that required some expensive bullsh*t school. Repeat after me, college for Information Technology is what we all call "easy mode". Certs and experience will always win a job over college.
Third. Sir, a diagnostic is a diagnostic. If the geek squad pimply faced kid was a surgical technician and your problem was chest pains, he'd easily charge you several thousand dollars to run diagnostics on your chest to see if it's gas pain or a freaking coronary. Users like yourself commonly get upset when an initial 5 second look at symptoms produces the statement of a problem that has common like symptoms. Why? Because you're cheap, you don't want to KNOW what's required to maintain and fix your machine, and then again, you don't want to PAY someone else to KNOW how to fix and maintain your machine. The problem is with you. Not the pimply-faced flunky behind the geek squad desk. If you don't want to pay money to fix your machine, don't buy one, or learn to do it yourself. If you think these machines should work without any flaw whatsoever, I challenge you to make one that does knowing that millions of people smarter than you or I have tried to do that since the computer was invented.
Fourth, A hard drive is made of several moving mechanical parts. A hard drive is electrostatic sensitive. A hard drive is magnetically sensitive. That being said, you should understand that even the slightest speck of dust can carry an electrical charge that will render your hard drive completely useless should it hit the right point on the hard drive circuit board. It's rare that this can happen but it can happen. Dropping the hard drive can cause the platters to fall out of place. Hard drive defects happen, and you need to understand that equipment with moving parts like that can, and will eventually fail due to age, mishandling, or misuse. It's a fact of life.
Perhaps the idiot at the geek squad desk doesn't understand the problem well enough to explain it to a user that doesn't understand that such a problem could even occur, but ultimately the responsibility falls on you to understand that you need to know exactly what is wrong with your machine before you pay.
For the record, if you picked on a nerd in high school, this is your kharma. We run the world now. Accept it.