The pitfalls of using a smartphone in public can be hedged about with various points of etiquette - using an email filter, saying no to the Robocop look of cordless headset, avoiding the novelty ring tone, refraining from frequent glances at the gadget when in company.
These days, round-the-clock availability is the order of the day, and being inaccessible - even momentarily - is tantamount to a dereliction of duty.
Smartphone users argue that, in this era of 24/7 business, when minute-by-minute developments must be monitored, both dinner table politesse and a notch or two on the blood pressure monitor has to be sacrificed if they are to keep in touch when they're out of the office. Yet the sight of a corporate lunch party, all casting furtive glances at their little friend, lined up beside each plate like a modern-day napkin, is both laughable and more than a bit sad.
Observing smartphone etiquette will go some way towards mitigating the offence, but there's a simpler, more draconian conclusion. If you are an smartphone user then you clearly have no time off from work and you can't socialise - therefore you should not attempt to have a social life.
Think of your friends. Their attempt to integrate you and your smartphone is as if they are hanging around your desk, talking to you while you are trying to get your work done. This would be rude in an office environment, and it's equally rude in a social situation. So help your friends not to be rude - just have a double date with your smartphone in the privacy of your own home or office.