Currently, our team is spread out between Ft. Collins, CO, and Orlando and Jacksonville, FL. While things have not gone terribly wrong having dispersed team members, I have noticed a difference in communications. The difference is that in the Ft. Collins office (and I'm sure in Orlando and Jacksonville), there is a lot of informal communication that occurs amongst collocated team members. You know, the kind of discussions that happen spontaneously. When these happen, a lot of project information gets passed between team members that doesn't get transmitted to other remote team members. There is no malicious intent to not communicate. It's just that the impromptu discussions don't usually inspire anyone to dial in to a teleconference number and all that...precisely because they are impromptu.
On the flip side, the scheduled daily stand ups, planning meetings and reviews all happen when they're supposed to and everyone communicates on those calls. However, I have found that something is lacking on those calls as well. When a team is all together in a room, there is definitely a different dynamic than when there are "voices" on the phone. Body language plays a huge role in communications and tells a lot more than than what people are saying. However, what I find really absent is the sense of team and camaraderie that exists in a collocated team. There are many "physical" exercises that we used to do for planning meetings and retrospectives that have been lost due to collocation. I found those really useful and without them, I think our planning and retrospectives are less effective than they could be. Maybe we just need to adapt those exercises to be more amenable to the space between our team members.
All in all though, I think I would definitely be in the camp of folks who believe that collocation really does matter. It build a better sense of team, increases both verbal and non-verbal communications, and really fosters a more collaborative work environment.