That's a great list but it's really hard to distinguish between fully nomadic (Buffer is the perfect example) and companies that hire many workers remotely. I think most of the listed companies hire remotely (ex. Trello) and have big distributed teams.
I am hugely interested in more examples like Buffer.
We're small, bigger than 5 of course, but small. Been
distributed for 18 years, we tried office space for the
bay area people and eventually went 100% distributed.
We've got people on both coasts of the US as well as the
middle (not sure if we have anyone in MST but we have all
the other time zones covered). And people in Canada, eh?