Jason Fried posts on the 37 Signals blog:

Technology is making it easier and easier to interrupt people — both virtually and physically. Well, they used “collaborate,” I’m using “interrupt”.

I was put under pressure at a recent gig for not being interruptible by phone or IM. Interruptions were an endemic problem at the place; people often complained that they could not make progress with work during normal hours. I chose to opt for core periods of productivity.

I did worry about how my actions sat with the Agile principles of communication, but concluded that I had to balance staying in flow with constantly having to chat with and answer non-urgent queries from remote colleagues. Ultimately, it’s all about getting things done.