Last month, when I first learned of Whisper, the app for sharing your secrets anonymously with strangers, I felt like I was late to the game.

The six-month-old iOS app had already skyrocketed to 1 million users, who had driven over a billion pageviews. Oh, and they're paying $5.99 a month to use the app, too.

I wasn't alone in feeling late -- Silicon Valley hasn't discovered the LA-based company yet, either. Except for Jeremy Liew, that is. His firm Lightspeed Venture Partners led a $3 million investment into the company with participation from LA entrepreneur Brian Lee, Joe Greenstein, CEO of Flixster, John Hadl of US Venture Partners, and Trinity Ventures. Notably, Liew was an early investor in Snapchat, which went on to raise $13.5 million from a long list of Valley VCs. Whisper's adoption reminded him of Snapchat.

Whisper's obscurity is about to change. Just one month since we first covered the app's funding, Whisper has already doubled its user base to nearly 2 million. Now, it's launching on Android. After two days in the Google Play store, it's gotten 50,000 downloads.

The app's popularity (particularly with college students) is driven by a couple of things. For one, Whisper users communicate the new native language of the Web: text over images. Created by LOLcats and proliferated by all of the most engaged Facebook pages, the image plus text formula is the most sharable way to spread ideas online.

Secondly, Whisper is popular because it is anonymous. Like a digital version of the art project PostSecret, Whisper allows people to emote online in a way that won't ever be tracked to their permanent, cant-be-deleted data trail left by social media accounts. As I wrote in April:

(Founder Michael) Heyward designed Whisper to let people take down the facade of perfection, anonymously, and just relate to one another. “You dont have to be this brand manager,” he says. “It’s exhausting.”

The most interesting part of Whisper is the fact that, unlike most of its social media peers, it has a built-in revenue model. Users want to emote anonymously, together. They're willing to pay to do so, to the tune of $5.99 a month or 99 cents per message stream. Now 800,000 paid messages are sent each day through the app. As I said last month:

It speaks to the Web’s deep-down desire to stay anonymous, despite Facebook and peer-to-peer services emphasizing real names and reputations. The size and power of fiercely anonymous sites like Reddit tell us there will always be a place for anonymous Web interactions. Hell, the original emotion-based social network, The Experience Project, has 10 million users sharing their anonymous secrets.

Whisper is a mobile version of that which happens to have a revenue model. (Post Secret is an art project; Experience Project is a non-profit.) Given the sometimes sensitive nature of the content shared on Whisper, the company has also created its own non-profit called Your Voice , which aims to reduce the stigma of issues college kids deal with, from eating disorders to anxiety and depression. "The idea is that it's better to use 'your voice' to share something then keep it locked up inside of you," Heyward says.