That's the problem with
large open plan offices. The only way for it to be workable for everyone is if everyone shuts up. I find it incredibly stifling.
My ideal environment is the team I'm working on in one big room, the music going, everyone jamming on the project together. Getting shit done. That's probably what Zuckerberg et al remember from when they started the company, and that's why they want to recreate it for 3,000 people.
Unfortunately, once you have more than 1 team in the room, it breaks down. You just shipped something awesome and want to shout about it? The other team gives you dirty looks and want you to just STFU because they're 3 days from shipping and in total crunch mode. Some people just like quiet all the time, they'll give you a dirty look when you get noisy.
Thus the big rooms of people end up being completely silent, it's the only way to make it work. They are terrible for collaboration. The only conversations happen in conference rooms, otherwise you disturb 100+ people.
In my mind small rooms, holding 4-10 people, are ideal. Each team gets a room. If the team likes it quiet, it will be quiet. If you want to bounce ideas around, you can do it without feeling like you are disturbing other teams. If you want to play music, you can play music. I think it's the feeling that the open plan offices are going for, but people haven't connected the productivity of open plan office with the actual size of the open room yet.