why would you have a massive 50lb heatsink
You wouldn't. 50lb is the maximum loading. If the computer is dropped and hits a hard surface, that could easily be exceeded.
In the days of metal can TO5 and TO18 transistors, the maximum safe impact was stated as around 300g, which sounds a lot till you realise that this could be exceeded by a transistor falling off a desk onto a concrete floor. In the same way, for a 500g cooler to apply 25kg of force on a motherboard only requires 50g. That means that if there is 1cm of give due to packaging, dropping it from 50cm will exceed the limit. If the motherboard itself is dropped directly onto a hard surface, with perhaps only 1mm of give, a 50mm drop will do it.
Biting the hand that feeds IT
