Yeah, until I started working from home I hadn't had walls for a decade.

I had an office for a short time. We were moving to a new building and got to pick our seating arrangements by seniority. I was toward the end of the list but nobody had picked the lone office in our area so I did. My manager immediately had the walls torn down.

Then how do they know you are working? (more importantly, how will they know they can interrupt you?)

Open floor plans can be a double edge sword buddy

Yes, exactly. When you sit right next to your business users and listen to their day-to-day activities or phone calls, it is priceless "ambient information". However, if you sit next to completely unrelated, but noisy team, it is hell! The trick is floor layout. The best companies in my experience obsess about floor layout to get relevant teams close!

In my experience as a software dev the "ambient information" that has tended to be most valuable was information about how the product was doing financially. I worked in an environment where we all had offices with doors and it was great but the "ambient information" I missed was that the sales of the product weren't going all that great and there were layoffs on the way. In a cube environment I think I would've heard a lot of chatter about layoffs coming weeks to months earlier. In this case I was pretty much blindsided.