I set the laptop down on top of an uneven stack of papers and I think the air holes were blocked underneath (at least that's one explanation, not 100% sure it's the right one)...
It took me about 2 minutes to figure out what was going on and to shut the computer off. Is the louder than normal noise from the fan (besides being a manifestation of my idiocy) a design feature to warn you that it's overheating, or did I damage the computer? The fan was almost shrieking...way beyond just a loud hum.
It seems to be fine now, but I hope the fan is not compromised. Any opinions on this? I got the computer at Costco and paid for an additional warranty.