An obvious benefit is that you can avoid the ridiculously expensive cost of living in the valley and set up in one of these nice places instead: https://nomadlist.com/ . You can also benefit from a larger talent pool and provide a nice perk for your future employees.
On the other hand I cannot see how team communication/ productivity wouldn't be impacted. Buffer has done it in a nice way but can it be scaled/replicated for any startup?
What do you think? Would you like to setup your team remotely? Already made the step?
I've built three successful teams remotely and I wouldn't trade any of them for one in a shared space. Use Slack for real-time, text-based communication, Google Hangouts for face-to-face chats, ScreenHero for remote desktop sharing (e.g. for pair programming or quick demos), Pivotal Tracker (or similar) for task tracking and weekly check-ins with every employee. If someone seems to be dropping the ball or losing focus, bring it to their attention and ask what's going on.
TL;DR: Communication is key. Not everyone's suited to remote work, but neither is everyone suited to sharing space. With the right tools in place and a dedicated team, you're all set.