Free Address Office

I know many companies have implemented a "free address office." Our company recently started experimenting with this concept. Since many employees are accustomed to having fixed desks, there have been numerous complaints and a strong reluctance to change. One of our purposes in implementing a free address office is to encourage employees to communicate more frequently, especially beyond their own sections or departments. However, I’m not sure if this approach is the best way to achieve that goal. What do you all think? If your company has adopted a free address office, what were your objectives? If the goal is to improve communication, are there other effective methods?