I promise this will be my last post about cell phone vibrate mode :-)
The biggest problem with vibrate mode is that people don't use it.
The second biggest problem, for me, is setting it and then forgetting to unset it which can result in missing calls.
Currently setting your phone to vibrate mode is binary, you do it or you don't. Wouldn't it make more sense to tell your phone to go into vibrate mode for the next hour?
Imagine a configurable go-to-vibrate-mode-for-n-hours option. Set it for 1, 2 or 3 hours and from then on when you went into vibrate mode it would return to normal mode when the time expired.
Fewer missed calls...and maybe fewer lost phones. Ever misplace your phone and then try to call it so you can find the phone by listening for the ring? This doesn't work if your phone is in vibrate mode (which Murphy tells us will always be the mode its in when you lose it!). With auto-vibrate-reset this problem goes away.
Ok, I'll get back to discussing software, cognition and philosophy now. :-)