Whilst we all love to hate overcrowded offices, I really don't think that there's any problems with open plan offices. I worked in those for 4 years and never had an issue with them. Sure, there is a slight decrease in your personal productivity due to the likelihood of distractions and interruptions, but that is balanced by an increase in team productivity thanks to an increase in communication.
Work is not all about your own personal work. In fact, in the large organisations where I worked, I'd say at least 50% of the work that people ended up doing was a result of miscommunication, and so there are clearly huge benefits in finding ways to decrease that miscommunication.
Even programming work was largely dependent on communication. The projects where I worked didn't do any rocket science that required weeks of solitary work to chew through, but it did require a good understanding of arcane, bizarre business (finance) rules and interface requirements, and the bottleneck there was definitely communication rather than concentration.