Several times, I've been talking on my cell phone with someone, the conversation has ended without my knowing it (such as being cut off, or the other person forgets to say "goodbye" before hanging up), and I've wasted some of my prepaid minutes either talking to a dead phone, or waiting for the other person to say something. I really wish that there were some kind of dial-tone simulation on cell phones, just to let the user know to hang up.
Obligatory old-guy line: "In my day, you could tell when conversations ended. What's the world coming to? Durn kids...."
(Well, the front page DOES say that we can talk about ANYthing here.)