started a fascinating little discussion about why people are irritated by cell phone use in places where face-to-face conversation would be perfectly OK (that is, not in a movie theater or library, but, say, in a restaurant or grocery store). His first guess was that it was a holdover from the recent era when mobile phones were a luxurious ostentation, but that doesn't sound quite right to me.Speaking personally, it doesn't annoy memuch, butin the first comment said what I was going to say, that many people reflexively talk much more loudly into telephones than they would to a physically present person (even though this usually does no favors for the transmitted sound quality). I wonder if this is correlated with the phone's audio volume setting--maybe if the voice at the other end sounds quiet to you, you'll talk louder to compensate. Another phenomenon thatmentioned is that cell phone conversations will sometimes cause people to tune out their surroundings and cause delays when, say, they're standing in line (though face-to-face conversations can do that too).But further down,proposed ainteresting and plausible theory, that the widespread annoyance at this has to do with our expectation of how a conversation sounds. If you hear two people talking to each other with the cadence and pauses characteristic of a conversation, it registers as "two people talking to each other" and it's possible to tune it out as not of interest (unless you're eavesdropping). If you only hear one side of that conversation, it doesn't sound like a conversation but like a series of disconnected utterances, and the "utterance possibly addressed to me" detector in your head triggers over and over and over. It makes some sense that the level of annoyance would vary greatly from person to person; when I'm concentrating on something I'm notoriously oblivious even to people directly addressing me, so this may not be as irritating to me.What makes me find this theory plausible is that I know how easily a tiny change in the timing of a conversation can derail it completely. If you've ever talked to somebody over a satellite link or laggy videoconferencing system that adds a quarter-second or longer delay to every utterance, you know what I'm talking about. Our social expectations about such things as the pause between statements in a conversation when both parties have something to say are delicately tuned.Maybe cell phones need outward-directed speakers that constantly mutter "mwa wah mwa" like an adult in a Charlie Brown cartoon. THAT will make them less annoying!