> The best solution is probably default closed offices with a culture of having your door open and lots of collaborating spaces that are actually used.
This is what I have right now at Microsoft and it's awesome. Everyone on my team has a private office, and we have plenty of collaboration spaces, including conference rooms as well as less formal gathering spaces between blocks of offices and near the food areas, plus a few large open areas dedicated for meetings (these are more isolated from offices, and generally used like conference rooms, but open to the hallways, with curtains that can be used to isolate a bit more).
This is what I have right now at Microsoft and it's awesome. Everyone on my team has a private office, and we have plenty of collaboration spaces, including conference rooms as well as less formal gathering spaces between blocks of offices and near the food areas, plus a few large open areas dedicated for meetings (these are more isolated from offices, and generally used like conference rooms, but open to the hallways, with curtains that can be used to isolate a bit more).