I think there's something inherent in working with people around you that you can't really replicate online. Being able to go over and talk to someone and ask them a question is invaluable when compared to having to message/email someone and wait for them to respond. It took us far longer to get sprint planning done (we were also doing Scrum) over the phone because no one wanted to talk, and that's easier to shrug off when you're at home. There's some level of team building that's missing when you telecommute - you don't go out for lunch with people, or have any sort of real social interaction.
Honestly I think it's up to the team/company to help work through those issues. We set up a chat system so we could talk during the day and that did seem to help for awhile, though.
In this, as in all things, your mileage will certainly vary. If you're a type-A people person, you should probably stick with a social context. Although (as elsewhere noted) you'd be surprised how much social interaction you can have online at home these days.
It's definitely an issue, and one that can be difficult to overcome. Since I'm splitting my time between my full time job, and working on Appleseed almost full time in the off hours, the last year has been short on social interaction, and I've felt the effects. That Oatmeal comic really hit home a few months ago when I went to a party a few months ago and found myself feeling very socially awkward. Not nervous, just a little bit clueless about what to do and how to do it.
I'm a very social person, so it was a little bit jarring how quickly those skills could atrophy.
But there are remedies. Scheduling social time is important, and not seeing as "wasted" time, but an actually necessary task for your mental health. Working in coffee shops when you need to, going for walks when taking breaks, etc. And going to a co-working space once in a while doesn't hurt.
The real need to get out is just a need to spend some time in the sunshine, or walking.. funny little things that happen on accident when you're commuting :)
Having been at an all-telecommute shop i can say that we ended up doing far more work than most teams. 10pm email conversations with the CEO were normal.
I found it far easier to do that, than to veg out in the office when I needed a break to go out, see the sky, walk around, breathe, etc.
Also, this was fairly early on, sphere was a new company and we were having growing pains. And its not like it was a nighlty thing, more along the lines of often enough to not be weird, but it wasn't often.
Also, before we were quasi-detelecommuted (meaning hires in NYC that went to the office) when something broke, everyone would pitch into fix regardless of hour. After the original peeps (well, most of us) left, the replacements (in the office) had an office mentality. That is, anything that happened after hours wasn't their problem.
Maybe that works better for them, but not for me. Doing things my way got more of my awake/alert time for actually doing things, and the flexibility it imparted helped keep me sane. Offices and rigid schedules drive me batshit insane.
At your employer's workplace, you don't have that control. You can be interrupted at any time by anything.
You don't appreciate that flexibility until you have to use headphones and music to drown out your co-workers' inane personal conversations.
In my case, though, I solved this by getting out to twitter/tech meetups and other activies (e.g. I'm speaking at a conference in Amsterdam in June). This occasional socialization is enough for me, though your mileage may vary. Also, it might help that I work in a very social open-source field where I can have continuous contact with other developers and community members.
I must admit, I would hate to go back to regular commuting. In my previous life I only had a 40 minute total commute but even 40 minutes is really valuable nowadays!