There's a conference call scene in this (relevant, interesting, funny) video which I think applies to this topic:

http://www.theonion.com/video/more-american-workers-outsourc...

I think that it could become a liability to do this at some point, though. When everybody is calling in and people have flaky quality, you are wasting at least some time. If a meeting is more effective in person, then have that meeting in person! You shouldn't be afraid to exclude one or two people if they're traveling; they're already excluded anyway. Why provide an illusion of close involvement?