Onstage at the Kravis Center, Palm Beach Opera is performing Rossini’s Cenerentola, the Italian version of Cinderella. In the second to last row of the house, 27-year-old Jennifer Pfaff’s thumbs are going a mile a minute on her smartphone: No evil stepmother in this Cinderella. Instead, it’s a stepfather baron who actually seems ashamed of his two daughters. #PBOCinderella.

Two seats away from Pfaff, opera newcomer Nate Mendenhall, 26, is also sending a stream of tweets to his 1,800 followers: I can’t believe I haven’t come to the opera sooner. #PBOCinderella.

Their phones shine like beacons from the back of the theater. But as long as they keep their ringers and photo-flashes off, they can tweet all they want.

Actually, that’s what Palm Beach Opera is counting on. Two years ago, the company became the first major performing arts venue in Florida to set aside free “Tweet seats” for the social-media savvy.

“People come and attend the final dress rehearsal of the opera,” says Palm Beach Opera marketing director Ceci Dadisman. “And they’ll tweet their thoughts, comments and also photographs of what’s going on on the stage.”

In the digital age, it’s not uncommon to have a live theater or concert performance interrupted, if not completely ruined, by a ringing cellphone or the glare of a smartphone. Many theaters implore audiences to turn off all digital devices. Ignore that request, and you’re likely to get dirty looks from other theater-goers and a warning from an usher.

But theaters nationwide have been exploring ways to draw in younger audiences through the use of Twitter, Facebook, YouTube and other popular social networking sites. And many South Florida venues have begun their own social media experiments.

Florida Grand Opera hasn’t tried tweet seats yet, but the company is encouraging live tweeting during a March 22 production of Tango & Maria de Buenos Aires, at The Stage in Miami’s Design District.

At the Broward Center for the Performing Arts, the policy is “cellphones off” during performances. But the theater has a Teen Ambassador program that invites a select group of high-schoolers to tweet before or after a performance.

While some major arts organizations such as Palm Beach Opera arrange for tweet seating during dress rehearsals, most are still are cautious about taking the plunge and creating in-house live-tweeting during public performances.

Just last month, New York-based social media expert Steven Tartick organized Broadway’s first-ever tweet seat event during a revival of Godspell. He says purists worry that their theater experience will be marred by the distraction of smartphone light or noise.

“The other concern that we heard from people is that this was diminishing the experience of sitting back and giving yourself over to the theater-going experience,” says Tartick.

There’s also the question of whether a flurry of tweets and Facebook posts actually leads to increased ticket sales. Adrienne Arsht Center vice president of marketing Andrew Goldberg says the jury is out on that, but potential theater-goers still like to hear from a trusted source.

“If you get a tweet from a friend, ‘You’ve got to check this out!’ you’re more likely to go check it out than if we tell you,” says Goldberg.

By that logic, even if just a handful of Pfaff’s 430 Twitter followers buy tickets, that’s a good day for Palm Beach Opera. And that’s not even counting all the re-tweets of some of her wittier messages:

The prince is enchanted by her beauty. Bippity-Boppity-Boo. Sorry. Couldn’t resist.

#PBO Cinderella.