I LOVED Abby's reply.
Funniest/saddest cell-phone-on-a-train incident I've witnessed: got on a commuter train waiting at the end of the line at about 11 am on a weekday, heading into downtown. Couldn't figure out why the conductor was hanging out in the seat behind me, leaning intently forward. About ten seconds later I realized the woman sitting about five rows up, facing away from me, was on her cell phone, alternating between weeping and begging the person on the other line, "Baby, please don't leave me today...." and screaming "you think I got myself pregnant?!?! Of course this baby's yours! I've never cheated on you, mother expletive-r" It was like Jerry Springer, entertaining in a horrible, sad, reality television kind of way. The ENTIRE car was riveted the whole way into downtown (45 whole minutes!), and when she made a particularly snappy comeback, all of us behind her were looking around at each other like, "Aw, SNAP! Oh no she DIDN'T!" That is the one and only time I've let a rude cell phone talker slide.