Mostly by very tight tolerances on certain components that causes them to fail prematurely. The difference between planned obsolescence and just cheapening out

Mostly by very tight tolerances on certain components that causes them to fail prematurely. The difference between planned obsolescence and just cheapening out on the BOM is mostly in the eye of the beholder. There's also the classic "software driven obsolescence", such as pushing a software upgrade that performs poorly on older hardware. Again, you could argue that maintaining older versions of the software is costly for the vendor and it makes sense for them to push their newer, shinier version. I think in many cases "planned obsolescence" is not so much about some evil corporate type saying "let's have this thing break on purpose two years from now" but rather some greedy corporate type saying "let's make this thing as cheap as possible".