There's a theory making the rounds that the MacBook Pro's high temperatures are attributed to a misapplication of "thermal grease" that's applied to the CPU and GPU chips during the manufacturing process.
A post by Interrupting Moss on the Something Awful forums mentions that "it just takes a slight misapplication of thermal grease on a MacBook Pro to make the temperatures skyrocket."
The amazing part is that if true, Apple techs are assembling MacBook Pro's with too much thermal paste because the MBP service manual tells them to! According to MacBook Pro service manual "0.2-0.3cc" of thermal grease should be applied to all three chip mating surfaces. Interrupting Moss however, states that reapplying thermal grease "properly" dropped the running temperature of his MBP by 14 degrees Celsius.
Jean-Cyril posts on the Apple support discussion boards that he "replaced the thermal compound with sparing quantities of Arctic Silver 5" and that "a small drop is sufficient."
MixedBag posted detailed before and after photos of his MacBook pro after removing the thermal grease and replacing it with "a fraction of a fraction of a millimeter thick layer of Arctic Silver 5 on the three chips." He goes on to say that it now runs much cooler.
The thermal grease modification is not for the faint of heart as it requires almost complete disassembly of your MacBook Pro. It will most likely void your warranty and most have said that it causes the fan to run more often. But for some it's a fair price to pay for a cooler running machine.
Should Apple have done this in the first place, or is the MacBook Pro designed with the extra thermal grease to keep the fan from coming on?