I work as an IT consultant at several small tech companies and startups in SF. Small sample of data, but here it is:

- 2 use cubicles (with a small number of offices, used by execs or for meetings or a mix of the two)

- 1 uses sort-of-cubicles which are mostly open and have low glass partitions (most would probably count this as an open plan)

- 2 use an open plan

As an aside, Apple customizes workspaces on a team-by-team basis depending on the needs and requests of the team.