One of the cool things about the HTC Touch Diamond is that if it rings and you are in a meeting you can just place it face down and it will mute the incoming call.

I really like this on my device however some folks don’t and if you want to switch it off then check out this article!

http://www.mydigitallife.info/2008/06/20/disable-and-switch-off-mute-call-on-phone-flip-face-down-feature-in-htc-touch-diamond/