Introvert programmer here. I find the opposite to be true. In an office situation, I'm much less likely to intrude on someone I need to communicate with, and they are much less likely to intrude on me. In an open environment, I get to overhear conversations that then demand my input. Yes, on occasion, I have been interrupted while attempting to formulate a very complex solution in my head, and yes this was frustrating. However, the benefit of all those overheard misconceptions and subsequent explanations vastly outweighed them.

That is why I firmly believe that given any team, it is best to have them collocated in a large but private room.

However, we are not talking here about the optimal location for any given group of programmers. We are talking about finding an optimal group of programmers without having to exclude those outside a 20 mile radius of your geographical location.