Fans? What fans?
Actually my home server (and router) has a power supply fan now. I went from a fanless power supply, which died, to this one. As luck would have it, one of the cables in my mini-itx case was resting against a blade. Our internet started acting funny and I went to check it out... I managed to see via SSH--right before it locked up--that the CPU was at 105 C. One hard drive was at 80 C (it didn't survive).
I don't even know how hot the source of all that heat was, the power supply, but I couldn't touch it for 10 minutes or so. When I managed to see what was wrong and move the wire away, the fan came on at Warp 9.
The power supply and my CPU survived (Atom 1.6GHz), which is amazing considering it was past it's critical temperature.
But now, even with the PS fan on, it doesn't get very dusty.
However, my GF's Core i7 in an Antec 300, on a carpet floor, with cats, gets clogged weekly!