Why Snapchat is worth $800 million

Snapchat

Snapchat has had a quick climb to becoming a high-valued, wildly popular social mobile app.

In less than two years, the self-destructing photo and video-sharing application has accumulated an estimated value of $800 million with about 200 million snaps shared per day, based on a recent valuation.

(Read more: Snapchat sees big future in erasable media)

Bill Gurley, general partner at Silicon Valley venture capital firm Benchmark Capital, said that while he's "absolutely" surprised at the value and number of users, it's consistent with the pattern that successful social networks usually follow.

"In the venture world, when these social network-type plays have taken off and generated immense viewership very quickly, it's typically been associated with a higher probability of a higher-price, late-stage outcome," he said at Fortune BrainstormTech on Tuesday afternoon. "And you combine that with what I would say is the loosest and most active late-stage finance markets, and I think that's the answer to your equation."

Snapchat's early investors include Benchmark Capital, Lightspeed Venture Partners and Institutional Venture Partners (IVP). IVP recently led a round of $60 million in Series B financing that valued Snapchat at $800 million pre-money. The company hasn't begun to make money yet, but investors see real strength in its numbers.

According to Onavo, Snapchat was used by 18.6 percent of all U.S. iPhone users in June. While Snapchat is still far behind Facebook, which was used by more than 72 percent of U.S. iPhone users during the period, it usage is not that far behind Twitter, which had a usership of 26.7 percent. And for a 2-year old company, Snapchat still has a lot of room for growth.

"It's one of the fastest-growing companies we've ever seen or been involved in," Gurley said.

Mobile users are flocking to the app because its ephemeral nature is in high demand, he said.

Snapchat lets users take photos, record videos and add text. Users set a time limit for how long recipients can view content before they're automatically deleted. The app is especially popular among younger users, as messages with a time limit offer privacy from adult eyes.

"We have some fundamental beliefs of why we think Snapchat's working. What we heard from people is that Facebook is LinkedIn to them. And what we mean by that is the permanence of it and who can see it," said Gurley. "It's their mother and their teacher and their neighbor, and they just wanted a place to communicate that didn't have that element, that lack of privacy."

—By CNBC's Cadie Thompson. Follow her on Twitter @CadieThompson.