From PC World
Smartphone Etiquette: Mind Your Manners for the Holidays
"Rule 4: Holiday parties are a time for socializing, not social networking. Seven out of 10 respondents think it's unacceptable to check emails, send text messages and make phone calls while in the company of others, let alone while on a date. And more than half said they would be offended if they were at a holiday party and someone secretly tried to tap the Internet at the table. I'm assuming they would include tweeting and playing Texas Hold 'Em on the iPhone as inconsiderate, too."
The Emily Post Institute is generally considered an authority on manners. Welcome to the new world of tablets and smartphones
Debrett's is another authority on manners.
Mobile Phone Etiquette
"Don't carry on mobile phone calls while transacting other business - in banks, shops, on buses and so on. It is insulting not to give people who are serving you your full attention."
I don't expect perfection from people and I've certainly been guilty of peeking at my phone while in a social setting before. I'm just requesting others to be considerate of how that distraction can be perceived by others.