Acutally, only seagates are surrounded by the rubber boot, and only the 5400rpm ones (7200rpm ones run too hot and melt the rubber over time)
Electro Static Discharge (ESD) is very dangerous for electrical components. Particularly circuitboards. Your HD is only liable due to the circuitry on the bottom/back of it.
When ESD happens, it can send too much voltage through the circuitry and cause burns/fractures in the silicone that short out the circuits. Ram is VERY susceptable to ESD.
When working on your computer, if you do not maintain a constant ground (for yourself) you risk ESD damage to your computer equipment. Just to give you a picture of how sensitive modern equipment is, a static discharge so small that you cannot even feel is big enough to cause damage. The circuit may not fail, but it could generate errors (causing BSOD's or memory seg faults).
At the computer maintenance shop where I work, we have an ESD video put out by apple in the early 90's. They had a voltometer measuring the amount of charge in the air as the guy raised his arm while wearing a sweater. Just by raising his arm, the voltometer jumped to a point 10 times more than what can damage a circuit. Thus the need for a constant ground to prevent that buildup by moving your arms when you work on your computer.
We have a specialized memory tester that does RAM checks for us to tell us if ram is good or not. We take old simms that we have no use for anymore and show people the effects of esd. Put a good simm in the tester, run the test and it comes up good. Take the simm, walk across the room ungrounded, hand the simm to another worker (ungrounded) they walk back and put it in the tester. Test the simm, and it generates errors in the tester. Put the simm in a computer, the simm works, the computer boots up, but after some use (as the memory fills with programs) things start freezing and the system will eventually BSOD.
What are the best ways to ground yourself when building? Do you place the PSU in the case, plug the PSU into the wall socket, but make sure it's switched off? And then touching the case grounds you and there's no need to worry?
Also, how do you guys advise setting up the components on the motherboard (CPU, RAM, etc.)? Is it better to put the PSU in the case, plug it in (keeping it switched off though), putting the mobo in the case, and then adding the components onto the motherboard? Or is it better to put hte RAM, CPU, heatsink on and then put it in the case?