The taboo against talking on your phone during movies is at this point about as socially established as our rules against eating each other alive, socks with sandals, or marrying our parents. But what about movie texting? Let's explore.
Rarely. People don't take kindly do these days, to the extent that they'll humiliate you with a pre-film PSA if you try and then throw a fit about it. But ye olde SMS does have its place inside the theater, believe it or not. Anything leading up to the show, it's entirely kosher to pull out the phone and tap away. Send emails! Send dongshots! Whatever! The lights are on, and your thumb-talking isn't diminishing the experience for anyone. As long as you keep your set on vibrate or silent, there's no reason why you can't go on a text spree. There's zero distraction. When the lights come down, however, it's time to put it away. You see, that giant, resplendent AMOLED screen? The one more brilliant than the sun's rays? It can be pretty fucking irritating to see that thing waving around during the middle of a film. Previews, however, are a grey area—be discrete. Text low, and text quickly. Turn down your brightness, keep your hand under your seat, and you should be fine.
Or, if you absolutely have to text during the film (what are you, a doctor, or a spy?), then act like you're hitting 3rd base for the first time, and send yourself into back row exile.
Once those previews are over, put your phone away. If you're on a BlackBerry, the tapping is really irritating. If you're on anything else, even the peripheral motion of sliding and swiping can be distracting to your neighbors. And if you really can't sit through two hours of entertainment without checking to see if anyone texted you, then you're facing far greater existential crises than whether or not someone texted you. Don't. Do. It. You'll inspire the wrath of your peers and perhaps the very theater you're sitting in.
Texting during the movie. Not okay. But the covert phone check? Yes. It goes like this: slide 'er out reeeeeeal slow-like if you feel the telltale vibration. Go ahead, check who it's from—but don't take the whole device out. Just the tip. Just enough to see who buzzed you. If it's important, scoot outside and reply. If it's not important, slide 'er back in. Just be subtle.
You can text when it's bright. Don't text during the movie. If you want to ninja-check your phone, be quick about it. And yes, the same rules apply to email. In fact, the same rules apply doubly to email.