Well, I'm torn on this. My initial, non-thinking reaction was one of rabid agreement. This is very correct if you're a 9to5er. If you are at the office to put in your 40 hours and then leave, I would agree that there is no room to inject a social life into this. There's also the issue of breaking flow, which you alluded to.

I think the typical startup lifestyle changes this a bit, though. We who run startups( generally )don't work 40 hour weeks, and if you're even a bit extroverted, chances are you're going to need to "get energy" from social interaction with your coworkers, since time to do this outside the office is fairly limited.

With the standard introvert archetype, this is likely a non-issue. My money is on samtp being an extrovert, and you( and I )not capable of empathizing with the odd need they have for such interaction.