Wait so Twitter allows corporations to access and search public tweets, which are published by people so that they can be seen publicly? Oh the humanity!
Next thing we'll learn some company is indexing public websites and allows people to search in those too!
Not sure how Zuckerberg being rich matters, but at least in FB case one could argue that social graph data - i.e. list of friends - can be considered at least somewhat private (not sure about FB settings but looks plausible). Content of public posts is definitely not private without any doubt.
Next thing we'll learn some company is indexing public websites and allows people to search in those too!