First read about this on adfreak: Kraft just launched a new semi-brilliant website/campaign which shows what happens if you don't have Mac & Cheese handy, but instead want to blow other things up in a microwave.
Similar to the Mentos experiment on YouTube, I think this is great example of viral marketing and the power of online video. Who doesn't want to watch stuff getting blown up in a microwave? I'm going to forward this around to everyone I know. Especially with snazzy music and a countdown timer to impending doom. The only reason I say "semi-brilliant" instead of "brilliant" is that the could have picked cooler things to explode.
Even though they say do-not-attempt-at-home, I'm sure this is going to spawn a whole series of knock-offs.