On the left side, about an inch in from the SD card slot, the temperature really builds up quickly starting first on the back of the device and eventually getting so hot on the glass it becomes uncomfortable to hold and to swipe. I've seen 48 degrees!
I have noticed this happening when using Dolphin HD browser and particularly if Skype is running in the background.
I wiped the tab, didn't reinstall from market and just loaded Dolphin and it didn't make any difference.
I'm guessing faulty device since there are only a few isolated reports of this online.