I was going crazy the first 6 months here because I was holed up in a office by myself with little in-person communication. There was no benefit to being in the office versus working remotely. My first attempt was to get the company a HipChat account for engineers to stay more connected. I even pushed for a couple of monthly engineer events so I would have an opportunity to interact with other engineers.
Open office setups can go horribly wrong. Never allow anyone who spends time on the phone into the open office setup. That stifles all interaction due to the need for silence. Additionally, engineers are forced to listen to a single side of a conversation that likely has nothing directly to do with the engineers. Project and account managers have a valuable job, and engineers should not need to be distracted by work that is not related to what they need to accomplish.
Additionally, I believe an open office for engineers should be reasonably small (4-10 people), and there should be some common responsibilities or projects between the engineers.
Other steps can be taken to give people the appropriate space for the task at hand. I've used a stand-up desk for the past three years. I hardly ever spend a whole day standing. I alternate between sitting and standing as my body gives me signals. Similarly, having quiet space (alternatively headphones, if desired) to crank on certain work can be useful useful. That said, three of the four of us have not used solitary space in the past 2 months.
Basically all of this is to say the issue is not black and white. If you prefer to work in a private office, like more than half of the engineers at my company do, that's fine. If you prefer to work in the company of others, that is fine too. Not everyone wants to work at a startup, and not everyone hates working for big financial companies.