Oh no, please don't start with the magical hallway conversations. I've never had a worthwhile conversation in a hallway or microkitchen, ever. This argument needs to die.
Having whiteboards around, I will see people talking about certain things or explaining some new system, and it's easy to jump in. Maybe these could be considered impromptu meetings, but they still have been great for me.
I'm not a developer, but I don't work with a group of people located in the same building, so all projects are de facto pretty remote heavy.