My family, friends, and people at church are always joking with me that I never respond to text messages and never return phone calls. I guess I should have been born in the last century or something; my personality is just not compatible with people who contact me electronically and expect an instant response. A lot of times during the day while I'm working, I turn the ring volume off on my phone, disable vibration, and flip the screen over on my desk. I just don't care like answering phone calls while I'm working unless it's work related.
I know it frustrates pausiepooh, as well. Most of the time my IM windows are minimized so I often don't see IM chat conversations until I tab to the applicable windows.