[PoetryInMotion]

Why are triplet carbenes not sp³ hybridized? Wouldn't that minimize repoulsion more efficiently than sp² or sp hybridization?

[spirochete]

There's a good full explanation here: http://www.chemicalforums.com/index.php?topic=28146.0

My quick and dirty explanation: generally organic molecules want to give filled orbitals more S character. There is more to consider then simply electron repulsion. I'm not sure if this is the best way to think about it but it rationalizes a lot of hybridization.