AUSTIN, Tex. — Ben Rubin arrived here completely invigorated.

For the past two weeks, the tech and media universes were filled with chatter about his smartphone app, Meerkat, which allows users to broadcast live smartphone video of themselves to all of their Twitter followers. He came to Austin hoping to build even more excitement around his app at South by Southwest, the three-week tech, music and culture gathering popular with early adopters.

He was in for a buzz kill. On Friday evening, Twitter, citing “internal policy,” restricted Meerkat’s access to its social graph. This meant that the people a user followed on Twitter would not automatically show up in Meerkat, severely curtailing the young app’s prospects for continued rapid growth.

But Mr. Rubin was not deterred.

“I don’t really care about being a hit at South by Southwest,” he said in an interview. “What was important for us coming here was to acknowledge the fact that we came from nothing just two weeks ago.”

Often, South by Southwest is described as a proving ground for start-ups, a way to test whether or not their apps will break away from early adopters into the mainstream. But for founders like Mr. Rubin, attending the festival is more about networking, meeting venture capitalists and other start-up founders.

Meerkat is in the process of raising a new round of venture capital, according to two people familiar with the company’s plans. Mr. Rubin did not respond to a request for comment on the company’s fund-raising efforts.

This has not always been the case. In 2007, Twitter had its “South by” moment, a tipping point for the company in which many people began to use the service more actively. Over a weekend, Twitter saw its message volume triple, to 60,000 per day.

The same thing happened to Foursquare, the location-based local discovery app. In 2009, Dennis Crowley, a co-founder, flipped the switch on Foursquare days before the conference began; it became the breakout app of the conference and was valued at nearly $100 million a little more than a year later.

But being crowned prince of South by Southwest is by no means a guarantee of success.

Six years later, Foursquare’s success seems to have stalled. Foursquare is not among the top 1,000 most downloaded apps in the United States, according to App Annie, a mobile app measurement firm. The company no longer throws lavish parties to court new fans at South by Southwest, as it did in the past. A Foursquare spokeswoman said the company had 55 million users and had seen triple-digit percentage year-over-year revenue growth, though would not talk specifically about its revenue figures.

Path, another social app, was famous for its South by Southwest presence just a few years ago, spending thousands on its hush-hush annual parties. The company no longer hosts its blockbuster events.

Kismet and Highlight were the apps to watch at the festival in 2012. Kismet ended up changing course to become a messaging app before being acquired by Yahoo last May; Highlight’s download score is not even high enough to show up in App Annie’s rankings.

For now, Meerkat is still enjoying its moment in the sun. Since Twitter restricted its access, Mr. Rubin said, Meerkat has seen the amount of streaming activity on the service double in less than 12 hours.

Meerkat is a top trending subject on Twitter in Austin. Reporters from news outlets like CNBC and CNN are using the app to broadcast live news to their Twitter followers.

Even if the Meerkat app keeps up its high profile at South by Southwest, Mr. Rubin has bigger problems to think about. Streaming video apps have been around for years, though few have caught on enough to win over mainstream users.

Mr. Rubin has tried for years to gain traction with Yevvo, another live-streaming video app. Yevvo eventually changed course to become Air, which is not entirely different from Meerkat, his latest and, apparently, most successful attempt.

“For live video, the bar is high,” said Justin Kan, a partner at Y Combinator, a start-up incubator. Mr. Kan shuttered his first attempt at a live show, Justin.tv, in which he live-streamed his life 24 hours a day, after the company failed to retain an audience.

“Most people don’t have 10,000 Twitter followers like the people who go to South by Southwest and stream video,” Mr. Kan said. “Live streams alone aren’t enough to sustain a service.”

There is also the problem of competition. Just a few weeks ago, Twitter purchased a Meerkat look-alike app, Periscope, for just under $100 million, according to a person familiar with the deal. The app has not been introduced at South by Southwest, but insiders using the invite-only test version of the service are singing its praises on Twitter.

People like Chris Sacca, an early Twitter investor and founder and chairman of the venture firm Lowercase Capital, say that now is the time that live-streaming mobile video will take off.

“We are going to see some of the most compelling, personal, memorable moments on the live video platforms that we have ever seen in our lives,” Mr. Sacca said in an interview. “Mobile is about to be intimate, emotional and more human than technology has been in history.”

Even Mr. Kan, of the failed Justin.tv video start-up, eventually found success. Justin.tv eventually became Twitch, a live-streaming video network focused on video game enthusiasts. Amazon acquired it for $1.1 billion last fall.

For now, most of this is out of mind for Mr. Rubin of Meerkat, who said South by Southwest was not about breaking out as a hot new app or proving whether or not live video will become hot with the festivalgoers. It is, he claims, about something else very dear to him: thanking his avid new fan base of more than 120,000 new users.

“It’s important for us to meet everyone who supported us from the start,” Mr. Rubin said. “They gave us so much love so quickly, and now we’ve created an early community.”