Ever turn around and ask someone to please be quiet?

i have shhh'd more than once. most recently at DDs school band recital. i give a tap on the shoulder and when they turn around i say "suush!" with a cutting motion across my neck. it's my go to move in that situation.

Yes, many times. I usually start with turning around and giving "the look". When that doesn't do it, I ask them to please be quiet. I've done it in movies, at the theatre and choir concerts. I actually did it once at a weight watchers meeting. I think it's extremely rude to talk when others are speaking, have some courtesy. You can catch up later.

OP you waited longer than I would have. I bet you got the stink eye from them too. Seem like people think you are the one being rude when you ask that!

I haven't.

I would be worried it would be the 1 in a 1000 that would lose their mind and commit violence.

I figure if the person had any manners at all, they wouldn't be talking over the program in the first place.

I said something to my BIL (adult) last weekend because in a room with 12 people and lots of hard surfaces, he started whistling. I'm no Sheldon when it comes to whistling but it was too loud in that confined space.

I try not to confront directly (though I will openly stare), but it takes Every Single Ounce of my self-control not to go all "teacher" on people who talk during presentations and concerts!!!

I did have to tell a mum to stop her toddler from kicking my seat at my dd's school presentation ... I said that she had to put him on her lap or move to the back ... she put him on her lap   

I've also given people who talk too much the evil eye at movie theatres ... yup, I'm a bitch   

No but back in my pre-home owning days I had loud neighbors next to my apartment and would have to ask them to quiet down at all hours of the night.

Have I ever?  For me it's more have I ever not!  This week in the doctor office, a woman comes in with her young daughter and teen son.  Son sat there on face time with a friend and was so loud.  Mom went back and left son with the little girl.  Finally I tried to get teen's attention and ended up getting up, standing in front of him and said, "You are too loud.  This is a doctor's office and people don't feel well.  Please speak quietly."  He said, "I'll go outside," and he stood up to leave.  I said, "You can't leave the little girl in here by herself," and he said, "Oh yeah." and he sat back down.  After about 5 minutes or so he started to get loud again and little sister told him he was too loud.  Then i got called back to see the doctor.

I work in a hospital where you would not believe how loud people are - housekeeping in particular.  Yelling to each other, yucking it up.  I tell them without hesitation to stop yelling - it's a hospital for crying out loud. 

I've also asked folks sitting in front of me to turn off their phones in movie theaters. The light is very distracting to me.

Uhhh yes? Many times...

Just curious, what was the name of the word game? 

Yup.  When I'm at the movies and people are chatting during the film I am not afraid to shush them.  Also, at a concert last fall, the couple next to me kept taking video and photos and yakking about it.  I finally  told them to stop talking.  Done and done!  When you shush someone talking during an event you're not the rude one.  They are!

The last event I was at the only solution would have been taking to the microphone and telling 90% of the people to shut up. It was a few weeks ago at DH's step brothers HS graduation (which is hilarious because we too have a graduate this year ). Anyways up until maybe two years ago graduation had been held for years on the football field and then for years at a local out door theater. At both venues people were always respectful and well behaved.

A few years ago it was moved to an indoor sports arena. The arena actually opens the concession stand during the ceremony. Not only was a steady stream of people getting up to get concessions but 90% of the audience held full on, full volume conversations the entire ceremony. One lady across the arena from us strutted across the arena from concessions, gabbing on her phone mid ceremony, walked to her seat and for the rest of the ceremony spoke on her phone. And yes, I did look periodically because I was shocked by it.

It was as if people were confused and thought they were actually at a sporting event as opposed to a graduation and they acted just like it was a sporting event.

My daughter graduates next year from the same school and I am already dreading the hideous behavior.

Yes. Especially in live events whether they are concerts, graduations, speeches, awards, etc. I think that is so rude.
I turned around during a school band concert once and told the person behind me that just because your child is not performing right now does not give you the right to talk through the concert. Other parents came to listen to their child. 
She called me a bitch and got up and moved. Her friend she was talking with just sat behind me the rest of the concert staring at the stage. 

Our son's band teacher got up at the year end concert this year and said "your children have worked very hard this year in band and want to show you what they have learned. Please turn off your cellphones and do not talk during the performance" She has been teaching band for 38 years and guests have become much less respectful.