The best theory I have heard and now believe is the blame placed on the oil squirters. Basically debris causes the spring to stay open all the time thus squirting oil at idle. With the oil squirters fully open at idle, there is a huge pressure drop causing lack of oil being fed to the main and thrust bearing. What do a lot of people do when they come to a stop or sit at a light? They are holding the clutch in. This in turn causes the trust bearing to take a severe beating because it is not getting any lube.