Curious about Rega Tonearm bearing damage

Hey guys, just curious. I hear a lot of talk about Rega tonearm bearing damage. "Carefull not to damage the main bearing", E.T.C. Even Rega themselves say not to upgrade wiring as this will cause excesive bearing wear in time. Just wondering how many bearing are there in the tonearm and most importantly WHAT are the main causes of damage or wear?

Thanks,
Balance