One of the listed StarCraft II Known Issues on the Battle.net Technical Support Forums is a bit of a doozy, as when rendering "screens that are light on detail" (such as menus), the game can cause hardware to heat up by refreshing the screen too frequently, which can put your system in jeopardy. The posting is from a couple of weeks ago, and the workaround they offer is clearly for the beta, but this known issue is also apparently still present in the shipping version of the RTS sequel, as a post on GameInformer.com describes the game's destruction of a graphics card and a laptop apparently thanks to this problem (thanks Ant via Digg). Here's the workaround for the beta, which will presumably work on the full game by using the proper directory:

Screens that are light on detail may make your system overheat if cooling is overall insufficient. This is because the game has nothing to do so it is primarily just working on drawing the screen very quickly. A temporary workaround is to go to your Documents\StarCraft II Beta\variables.txt file and add these lines:
frameratecapglue=30
frameratecap=60
You may replace these numbers if you want to.