Valve has a democratic horizontal structure, its doing very well.  I'd also argue they produced some of the best games ever made.  However they are run on deeply capitalist principles and that makes them exploit their users (as has been laid out in numerous articles by many people).   The problem isn't democracy (or even the lack of it) so much as capitalism, which encourages tyranny because being tyrannical is profitable - and its the same argument pro capitalists used against so called socialist leaders  - they become corrupted by  money.   But so do capitalists, which is why nobody can name a large high value corporation that does not behave tyrannical.