Twitter would be a formidable competitor if they had leadership that understood their own product. Zuck uses Facebook confidently and skillfully. There's the difference. Leadership of users, because the top guy is a user.

— Dave Winer. Zuck uses Facebook in a way — protective of his own privacy — that he works very hard to prevent anyone else from doing. It is true that Twitter's leaders don't use and may perhaps not understand their product, but the truly significant difference between them and Zuckerberg is that they aren't as ruthlessly, contemptuously exploitative of their users as Facebook is.