Hi,
I'd just like to point out that (though I appreciate there are plenty of people who probably do mess about with things they don't understand), it's a little unfair to assume that's what's happened to everyone, there may be an underlying issue with the software or hardware. I got my N900 on Monday, barely used it til Thursday (I was waiting for my old number to transfer to my new contract), and last night (without having played with the command line or done anything else out of the ordinary), I opened the web browser, the phone began rebooting before it opened, and hung after "NOKIA" displayed on the screen, now you have to pull the battery to switch off, and when you try to boot it just sticks at that same point (when the five blinking dots appear in the center of the screen). I had experienced it rebooting itself a number of times previously but (being used to Nokia Nseries phones) I kind of accepted that as a flaw to be fixed in a later software update.
Anyway, the point is, I've done nothing to screw it up, so it's obviously got a bug in something somewhere, and mine probably isn't the only one in existence that's done it. Don't get me wrong though, I'm not criticising the N900 or Maemo platform (actually whilst it was working I thought it was fantastic), but I think it illustrates that it would be handy if it could be "hard reset" easliy, it might be all mine needs to get going but as it stands it's going to have to go back to Nokia (complete with the few contacts etc. that I have left on it and can't delete).