A great one I've seen twice on the last train home is a couple who've sat in seperate carriages and argued via mobile phones taking it in turns to put the phone down on each other, before meeting up to carry on the argument face to face.
ps I'm a big fan of texting for when you've got a short simple message which doesn't need a reply..."I'm on the 1934 train from Euston" is the one I'm most looking forward to sending right now
