With over 50 employees the only model that ever worked is the one described by http://manager-tools.com/ :
- Between 8 to 12 direct reports/manager, never more than 12.
- Weekly 1-on-1 with EVERY direct report, never missed.
There's a way to flatten the structure somewhat with Team Leads managing up to 6 people: part development, part people management. Even then the Engineering Manager has to be hands-on.
This is how people work and it will not change anytime soon. Everybody needs weekly check-in with the company (represented by the manager) to stay in course. And everybody needs to know "who's the boss", even it it's not an official title or formal authority (think about Linus).
Citing Google as a good example is not too inspired. With all the billion $s they can't come up with one more product - it's still a single trick pony. There's Search/AdWords, everything else is pretty much failure in comparison. Maps is somewhat profitable, but it was bought from somebody else and it's pocket change next to Search. Everybody profits from Android, except Google. And then there's Google+, Wave, Health, Video, Buzz, Catalog, Froogle, Orkut, ...
So before trying out a Google-style manager-less chaos, make sure you have a couple billion $ in your bank account first.
And yes, when somebody is not calling the shots on who gets hired in his/her team, that's not a manager. They get the task (deliver the results) without getting the tools (pick your team). How that would ever work?