I can answer that. We changed the policy to allowing remote team members as long as they are primarily contributing to open source projects.
The problem with being remote is how much you lose in communication when working on a project. You don't have that problem with open source projects. The design mocks, discussions, etc. on Github are the same as anything someone in the office would see.
Also ... it just got to the point where it was stupid not to hire remear (Ben).
I've been working from home for many years and, work-wise, it was really not that different communicating with the team vs if we all were sitting in one room.
It is just the personal feel that is different. Things like you miss some side-jokes, which might not be that fun without personal presence; Hanging around after work; etc...
This was circa 2005, so as you can imagine the tools weren't quite as well developed as they are today. This meant that everyone had to make sure they communicated extra well. Rule of the road was that you were available on IM same time as office hours, you announced coming and going with an email to a shared distro list, etc. No rocket science.