What happens if MyEtherWallet goes down?
MyEtherWallet is not a web wallet. You don't have a login, and nothing ever gets saved to our servers. It is simply an interface that allows you to interact with the blockchain.
If MyEtherWallet.com goes down, you would have to find another way (like geth or Ethereum Wallet / Mist) to do what we are doing. But you wouldn't have to "get" your Ether out of MyEtherWallet because it's not in MyEtherWallet. It's in whatever wallet your generated via our site.
You can import your unencrypted private key and your Geth/Mist Format (encrypted) files directly into geth / Ethereum Wallet / Mist very easily.