I don't think more announcements are going to make one bit of difference. In most cases, there is already the box office reminding you to turn off your cell phone when you pick up your ticket, then the ticket-takers, the ushers, the slip in the playbill, and an automated announcement before the curtain rises and phones STILL go off. Too bad theater staff cannot treat audiences the way students in high school are treated by confiscating devices and then forcing patrons to pick them up in the lobby after the show.
"Mostly, I loved the size of these people's emotions. Nobody has emotions this size anymore. Outsized emotions. Operatic emotions. Kushemski and Vanda are like Tristan and Isolde, they're Paolo and Francesca. Nobody's in total thrall like this anymore. Nobody's overcome by passion like this, or goes through this kind of rage." Thomas, Venus in Fur