its not just folders, but DCers in general who have to monitor temps. as you can see in my sig, i have four single-CPU boxes. both of the 1055Ts are OCed, while only one of the 1090Ts is OCed. i keep them cool with CoolerMaster's Hyper 212+/212 EVO. i also have a 2nd fan added to each so that they operate in a push/pull configuration. as you can also see in my sig, i have 2 GPUs in each box, so the CPU isn't the only thing generating heat in these machines. take into account that many crunchers (myself included) run their hardware at or near 100% load 24/7 (and not just an hour or two a day, like the gamers out there), and it becomes very apparent that folks like us need above average cooling solutions.
aside from the aftermarket CPU coolers that i use, some of my GPUs also use aftermarket cooling in the form of Arctic Cooling products. my dual HD 6950's both use the Accelero Xtreme PLUS II, while my single GTX 560 Ti uses the Accelero Twin Turbo II. my dual Gigabyte GTX 560 Ti's use their stock WindForce coolers b/c the motherboard they're installed in allows for generous spacing between them. the HD 7950 and the dual HD 6670s use their stock coolers.
my cases aren't listed in my sig, but they contribute just as heavily to sufficient cooling as my other components. my dual GTX 560 Ti rig is housed in a Corsair Graphite 600TM ( the version w/ the mesh side for mounting four 120mm fans). my dual HD 6950 rig is housed in a Corsair Carbide 500R. my HD 7950/GTX 560 Ti rig is actually not in a case at all - its on a test bench out in the open. my dual HD 6670 rig is housed in a Rosewill Armor.
i should note that i'm also a silence freak, which is difficult for a cruncher to be, considering all the cooling one needs. that said, the Graphite 600TM and the Carbide 500R may not seem like the best cases for cooling out there - they're not. they're excellent, but there are better cases for cooling out there. that said, you're going to sacrifice silence when going to a better cooling case. it helps that my ambient room temp is ~71°F (22°C)...i live like an Eskimo. if i were more like the average person who leaves the thermostat at 75-77°F, these cases would still do a sufficient job of cooling, but i'd incur a significant increase in fan noise.