I found it interesting that, unlike Microsoft (and Joel's own company), Google does not give their developers their own private offices.
Are developers at Google as productive as they can be even sharing an office with 3 other people? Does it not matter if you are a certain caliber of programmer that shares an office with others of the same or similar caliber and level?
Perhaps those who work at Google have greater self-discipline and awareness to know when collaborating starts to cross the line into interrupting someone so the need for private offices is not as necessary as with other companies.