[jimbokun]

So what other software companies have private offices?

In addition to Stack Exchange, Microsoft was mentioned.

When I worked as a developer at Carnegie Mellon, I had an office shared with one or two other people (which was a nice perk, given the pay was much lower than industry).

Any others?

[ohast]

I believe http://www.fogcreek.com/, which is no surprise though since their affiliation with stackoverflow through Joel Spolsky.