sometimes i miss going into the office, but then i watch a corporate training taped in the office and remember how cold and alienating it felt. most days it wasn't a place where you bumped into people and had the much-vaunted spontaneous ideas conversations. most days it was very clean and very quiet. some teams even had "don't talk around here" signs up outside their area!
sometimes you would have a really good chat that opened up a new path, but i don't think hoping for serendipity is worth the cost of hauling everyone in every day