This quote "Isolation Kills Innovation" is on the Pragmatic Programmer's community page. And it's true. When we spend all of our time heads down doing any type of work, we lose our sense of perspective, we lose the new ideas. We tend to get stuck in ruts. The old saying "Can't see the forest for the trees" can be applied here.
So what if interaction is harder to come by? What if your company doesn't let you go to conferences? Maybe you don't have active user groups in your area. What are your options? As a consultant who generally works on project at home, this is real concern for me. Last week at RailsConf I realized how much I'd been missing that interaction. (I do have a great local Ruby user's group, but I'm talking about every day interactions.)