You can write anything that you would be able to write on a server and put it onto the blockchain. Instead of Javascript making calls to the server, you would be making calls to the blockchain.

I personally like hard forks. Particularly, I like the fact that they give users a measure of control, requiring them to opt in to protocol changes. Sure, they can be a little more chaotic if they're controversial, but that's the price of freedom.

When I came up with Ethereum, my first first thought was, 'Okay, this thing is too good to be true.' As it turned out, the core Ethereum idea was good - fundamentally, completely sound.

Vitalik Buterin Quotes