'Where would we be without mobile-phones?” asks one of your dinner-party guests. I usually respond with, 'We'd be a lot more friggin civilised.”

How often have you been talking to someone, a real three dimensional person, and at the first tones of their phone's usually ridiculous ring they answer it as if life depended on the person at the other end. Even worse is the answering of text messages, not only by snotty teenagers, but by so-called adults at my dinner table! I told someone just last week that if they continue to do this at my dinner table they'll be thrown out the door.
If you do decide to put up with this and hang around at this foul impertinence – you can hear a conversation about: what to pick up at the supermarket on the way home, or 'what are you doing?” This height of rudeness is the down side of personal mobile phones; that, and a bad-habit developing of talking rubbish.
Mobile phone use in the professional world has also become bad practice. Once upon a time people were on time, now many seem to take it for granted that their tardiness can be forgiven simply because they have the ability to ring you on the way – well they shouldn't, because I don't!
Also, many salesmen are scared that they'll lose a sale if they don't drop everything and answer their phones!?! What rot, it's simply a habit they've got into and can't go on living without that purping, tweeting, screaming nuisance by their ear. And, what about those ridiculous ear piece things? What makes them think they look cool and cutting edge? Give me a break, you are not a member of the American Secret Service!
I have a mobile phone – my employer makes me have it. I know, I know that sounds like, ‘my wife bought it for me', as in when trying to defend yourself when caught wearing sandals; but I remember what good manners are and what phone rules should apply (anything else deserves a flogging):
If talking to a person in front of you – look at them, use eye contact.
If your phone rings, excuse yourself and silence the thing. Don't answer it. Better yet, throw it in a rubbish bin, a fire, or a jug of water, or fish tank.
If the person you are talking to answers theirs – walk away, or better yet, call them on your phone and tell them what an ignorant, ill-mannered arse they are, and then leave.