For me, a big part of being happy and productive on a team comes down to how connected I feel; to project decisions and team members. And I think that sense of connectedness is largely a result of how we communicate.
For teams that are 100% remote, communication is pretty straightforward. Same for teams that are co-located. But for teams that have a mix of both, things get complicated.
I think the reason why is because the communication styles necessary to maintain sustained team homeostasis are very different. For example, remote teams tend to spend a lot of time in VC, chat rooms, and project management trackers where the majority of decisions are well documented and can be referenced later. The overhead is high but it's worth it because everyone experiences the benefits. Everyone stays connected in the same way. Co-located teams tend to make decisions less formally via spontaneous interactions. State isn't distributed as efficiently, but that's okay because overhead is low, and everyone keeps everyone else up-to-date (more or less). Again, everyone stays connected in the same way.
But when some decisions are documented and some aren't, when state gets unevenly distributed between digital tools and chance encounters, the folks who tend to miss out the most are the ones working remotely.
This asymmetry is what makes remote/co-located hybrid teams really tricky. WAYWO, Peer Roulette, G+, Hangouts, etc. kinda sorta work, but to be honest, since moving to Seattle, I haven't really found a good way to stay connected in any meaningful way other than traveling to MTV.
I think this is why many companies eventually trend toward one or the other. Google is a good example, as is Yahoo, and Reddit. Basecamp and GitHub are the only companies I'm aware of that encourage both, but Basecamp is notorious for enforcing remote-style communication even in their physical location and GitHub has only been around for ~7 years. I wonder if they'll have the same policy in another 7?
Sorry for the long email! This is something I'm pretty passionate about and wanted to share my thoughts on.