1. 8 people make less noise than 80 people.

2. Physical security and confidentiality is much better.

3. If teams hold 'stand up meetings' or suchlike without using meeting rooms, they won't disrupt other teams.

4. People who have to make calls all the time (customer support, sales etc) don't disrupt other people.

5. Fixed walls remove the temptation to salami-slice square-footage-per-employee, protecting good working conditions.

6. Climate control becomes simpler and has a better chance of working.

Up to 8, that's more of an upper limit.

Sound levels rise with the size of the crowd. More people making noise, more conversations more of the time, more space to spread the sound, and less individual accountability means people talk louder to be heard and are less considerate of their neighbors, creating a feedback cycle that ends up in a very rough environment.

I don't know how true this is for others, but on-task discussion doesn't grate on my nerves like random off topic conversations. If someone is talking about some aspect of the project I am working on right next to me, I can handle that MUCH better than someone in another department 4 cubes away bloviating about what their kid wore to prom or who the Piggers beat the previous night ("YOU SHOULDA SEEN IT MAN!!").

I know that isn't the case for everybody, but I think I'd be quite comfortable in an 8 person war room as long as folks were actually working on stuff.