Vaccari, the co-founder and CEO of , which ranked high on Mashable's buzz meter late Saturday afternoon, discussed Highlight, Sonar, and Banjo, which will participate in SXSW's accelerator competition.

"This has the potential to become really big," Vaccari said, citing investor interest. Social discovery could become as big as social networking, some people believe, "because it's sort of the natural extension."

But rather than whipping up more hype around social discovery, Vaccari pointed to a number of challenges with the apps.

Interest at SXSW is not representative of how popular the apps will be, because conference participants have come with the specific intention of meeting new people who share their interests, he said. So it is an open question how social discovery will fare among those who are less tech-friendly and more concerned about privacy.

Challenges include how the apps determine who shares interests, how they help facilitate real-world meetings "without being creepy," and and how detailed location information should be used to encourage conversation while still keeping users, especially females, safe, he said.