PC fan on 30 volts

[BrianG]

I think the designers rely on the fact that heat tends to travel from a higher concentration to a lesser concentration. The heatsink on top cools the top layer, which then "attracts" the heat from lower levels. I'm sure those lower levels must be hotter, but FETs conduct less the hotter they get, so they are self-regulating in a way. Of course there are limits, which is why some burn up.

IMO, they should add more heatsink area or more FETs. Adding FETs would do two things:
1: Increase current handling (duh :))
2: Decrease total output resistance, which in turn causes less voltage drop on the devices, which then reduces generated heat, and increases efficiency.