As I see it, most every structure works when you've got a fountain of never ending cash. The true test of a corporate structure is when that fountain starts to run dry or there was never a fountain to begin with. Facebook is hitting that wall now.

I think it depends on what “worked well” means.

They have stagnated product wise but it seems that their employees are happy and they make enough money to be profitable.

I think this is also a function of their competitors being jerks (Epic) or not really caring (Apple App Store). So a true competitor could likely eat their lunch if they really wanted to.

If valve didn't have access to free effortless money then it's informal structures might look very different by necessity. As of now there must not be much drive to change anything.