Different Strokes for Different Folks
I feel like it depends on the job type, and personalities. Different Jobs and positions require different amounts of collaboration and interaction between employees. I would imagine for a writer an open office would be very distracting and frustrating. Someone like a programmer or a graphic designer may enjoy it being able to easily get feedback and help from co-workers.
At my current Job we have two offices. One is shared by 4 employees at any given time. The other office usually is occupied by one person. This works quite well for us. With this format we can collaborate together, communicate, or have our private quite work time alone. I would think this format would also work well for large open office spaces with a greater number of employees.
Also I think having the CEO out in the open office is amazing. It must make them much more approachable. Or maybe it just adds stress thinking your boss is always over your shoulder.