I think I noted before that I've only ever heard the fans in my MacBook Pro spin up once or twice under high load. Otherwise, it seems about as quiet as my old PowerBook G4. Yesterday, reading mail while watching television, with the MacBook Pro on my lap, it seemed to be really cooking. Really cooking—the case was hot on the undersurface, and at the rear on the top, near the display hinge. I had felt it heat up before, but predictably, under load. I wasn't really doing anything, yet iStat pro was reporting a CPU temperature over 70ºC. This seemed ridiculously high.
/usr/bin/top was unhelpful: top itself was the highest CPU user at about 4 or 5%. I got distracted for a while by Google: "macbook pro cpu temperature" yields some 143,000 links to people obsessing over this very problem. I briefly checked out smcFanControl, which I used to at least ramp up the fans past 2,000 RPM while I sorted out the cause of the problem. What I did discover was OS X's Activity Monitor. Evidently it's a better top than top:
See all that colour under "CPU Usage"? That's bad. Whatever DirectoryService was doing there, it stopped after a reboot. And my CPU is now running in the low 40s.