From a Rhizome thread:
Well, that’s easy: we control the time of TV and email but not of telephones. You’re supposed to answer the phone when it rings. No one expects you to answer, or even read, an email instantly.
The first time I didn’t answer my phone when it rang was when my baby was born. No way was I going to interrupt breastfeeding or lullaby-singing or changing a nappy to answer a nagging phone! My sister-in-law was appalled. She truly felt that one has a moral obligation to pick up a ringing phone. No matter who was calling.
I still ignore the phone if it interferes with reading a bedtime story to my daughter, or I’m doing something else important, and I turn it off sometimes – but though I feel little guilt at that, I feel absolutely none at doing the same with my mobile.
And I love SMSes. They’re polite. They wait for you to have time. You can send them and know that you’re not interrupting. And you can answer them instantly if so inclined.