I never worked in my own office (I'm 39), so I'm really curious what you prefer: phone, email, knocking on someones door?
Also, how do you stay in the loop about what's going on?
On the flip side, most of the day my door is open, and I don't mind occasionally being interrupted to help someone else with whatever they need. If I have a conference call or I just want to really focus on something, I close my door and it's unlikely anyone will knock or otherwise disturb me unless the building is on fire.
My team is distributed around the world so my team collaboration is all virtual, although my management and some of my [internal] customers are located in the same building as me so they can stop by my office or vice versa if we have things to work on together.
It's a wonderful, comfortable way to work. Your ability to concentrate is respected. It's overall a much quieter environment conducive to solving problems. You'll loop in yourself during lunch, at meetings, getting coffee, passing by other offices/being passed by, etc.
Since most team communication happens over IM, it's easy for anyone to read back on what they missed. Most teams also do daily stand-ups or other meetings, to catch the larger group up on anything important.
FWIW, all the places I've worked that had offices in whole or in part had a culture in which everyone left their door open unless they didn't want to be disturbed for some reason. Collaborating was never an issue. If everyone always kept their doors shut, I think I would have found that hindered communication, esp. pre-IM.