I sometimes use smileys in my e-mail, and perhaps you do too. Also called emoticons, they're those little faces made up of keyboard characters meant to show irony or humour or whatever. So if I sent you a message saying something bad and I put a :-) at the end, it means that I don't mean what it looks like I've said. It's sort of the equivalent of speaking in a sarcastic or ironic voice.
That's one of the troubles with e-mail. It's all written in the same voice so there isn't the equivalent of inflection, a laugh, a whisper or whatever. Some of you might be in the habit of using bold, italics or even underscore to show what you mean, but these things often disappear when messages are going between mail systems, and are transferred as plain text.
If you want to shout at someone, write everything in caps. That's what Barbara (our general manager) and Terry (who handles PR for Harvey Norman) do. They don't mean to shout, but they leave Caps Lock on all the time.
A second problem with e-mail is that while the message is clear in your mind, it may come across with a totally different meaning. Your polite reminder that something hasn't been done is perceived as a violent rebuke, precipitating the e-mail equivalent of an Exocet missile exchange during the Falklands War.
A third problem is that you DO say what you mean. The trouble is, once it's gone, you wish you could get it back. If you're telling someone off to their face and they start to dissolve into tears or reach for a handgun, you can change tack immediately, or at least soften the impact of what you've just hit them with. E-mail doesn't offer that luxury, though a "seek and destroy" utility would probably sell well.
Yet another problem with e-mail is sending terse, cryptic answers to messages that the other party has already forgotten about. If you suddenly fire off a message saying: "Yes. Especially if they're single," the recipient probably won't remember that in the middle of the e-mail they sent you last week, they asked if you've ever bought red roses as a surprise present.
So that's why this week is national "Ring Someone Instead of E-mailing Them" week. That way you can leave a cryptic voicemail instead!