Some guys just want to watch the virtual world burn.
There's a certain devious pleasure in spending hours creating a structure to be destroyed. It taps into that same instinct you have as a kid building up blocks then pretending you're a monster savaging the city.
But blowing up buildings in Minecraft seems especially ridiculous to me. First off, the server lags pretty regularly during the explosion, so it's not like a you are watching a smooth, vivid explosion. Second, it's not a first person shooter where there's this viseral, graphic payoff. Even big explosions in Minecraft are still 3d blocks. Still, there is something about watching someone blow up that which they've just spent hours creating that is so much fun to watch.
Big Ball o' TNT
Making the Servers Yell
Death from Above
TNT City - This video has so much potential, but no actual explosion.
Although not the biggest, this guy's explosions are probably the most fun to watch.
The Quarry Maker.
The Pit Digger
This video probably has the most ridiculous explosion results of all of them.