It all depends. There's lots of old guys here so they're probably out of touch with current society.
If you're on a date: no phone
Business meeting: no phone
Family: your choice, they won't cut you off anyways
Lunch/dinner with work mates: totally fine
Large seminar/social event with tons of people: totally fine
It also depends what you're doing on your phone/ipad. I get emails a few times an hour and calls non stop between 9am and 6pm. I'm not going to try to make someone else happy and potentially fuck myself over with work because they think it's rude. Same with my gf, she understands that I pay for almost everything and I'm paying for the dinner she's about to eat, so she better be cool with me taking calls/emails while we eat or otherwise she can foot the bill for everything from now on.
Edit:
I also goto a lot of sales/business/marketing seminars and at every single one as I look around every single person has their hands under the table playing with phones.
We stopped checking for monsters under our beds when we realized they were inside us.