I'm honetly not sure how blockchain.info doesn't ahve your private key. They need it to do anything.
I think they store, on there servers, some peice of data, that when combined with your password, turns into the
private key
That's my point really, as far as I know they have all the information needed to empty my wallet.
No, they do not. They have only the encrypted private key. It can not be used without decrypting it. The encryption is done by you (by your browser) using javascript, and only the encrypted private key is sent to them for them to store in their database.
I do not know them well enough, and I guess the same could be said about any bank in the world.
You don't need to know them. The code is open source. You are welcome to read it (or hire someone to analyze it for you). Analysis of the source code makes it clear that the unencrypted private key is not supplied to blockchain.info. It is also clear that the password is not sent to blockchain.info.