Email in your pocket
A few friends of mine have a BlackBerry or some other push e-mail device (including the iPhone). Having dinner with them just isn't the same anymore: they're checking their e-mail just as often as I am, when I am working on my laptop (which is way too often). It made me kind of relieved that I don't have push e-mail. Somehow the different modes of reaching me help me in filtering out the urgent messages from the stuff that can wait.

Message Mode = Urgency
> Urgent: call me on my mobile (the people that are important have that number).
> Somewhat urgent: call my office phone (if I'm not there, a colleague will pick up, if it's important, they'll give you my mobile number).
> Somewhat urgent + personal: send me an SMS text message. Usually I'll get back to you pretty quick.
> Not urgent: send me an e-mail. If it's directed to me personally, I'll respond (in time). If I'm in the CC I might ignore it.

"Sent by BlackBerry"
People know that I won't respond to e-mail messages right away. However, if you have a Blackberry, and people know this, they will start expecting you to respond to email during the weekend, or at ten in the evening. It might be me, but I'd rather have the people on the other end of the line do a little thinking (how urgent is this message) and then selecting the mode to reach me. I'm not saying that I won't use e-mail on the iPhone (it's finally coming to the Netherlands), but my messages definetely will not include a line like: "Verstuurd met BlackBerry van KPN" (sent by BlackBerry from KPN). For one, that's advertising and doesn't belong in my emails, and secondly, it disrupts my message mode filterting system: all of a sudden people know I can check my email over the weekend.