While I appreciate your questions I get the feeling that your trying to poke holes in a very well researched and funded project based on what you read of it in my comments.

There's much more to the project and a lot of brilliant people with over a billion dollars in funding making sure this thing is bulletproof. So if you're interested in learning more about it I'd recommend you read their whitepaper as it will be a much better source of information.

However to quickly answer your comment, the 21 are elected by vote and are easily replaced by vote from the users they serve.