Has it ever happened to you? Your friend or colleague sent you an amusing email. You quickly composed a clever riposte. You clicked "send". And then you had second thoughts: Oh dear, I forgot that X is a little vulnerable in that area; she might take it up the wrong way; I wish I hadn't sent that message.

It is so easy to forget your manners when you are not dealing with people in the flesh, or even on the phone.

There were two bombs in the news this week: North Korea's underground nuclear weapon test, and the population explosion - as some see it - that brought the number of people in the United States to the 300 million mark, and past it. It is hard to guess which caused more gloom in the office of Population Connection (formerly Zero Population Growth), which churned out a press release bemoaning the effects of growth on the environment and proposing a four-point plan for stabilisation.