Developers hoping to cash in on the app gold rush today face a harsh reality. Competition is fierce, standing out can seem like an impossible task and well-heeled companies are capable of producing bigger and better apps more rapidly than ever before.

Even so, app store success stories like keep developers going.

Sucess stories like Draw Something, an iOS and Android app which The Verge describes as a “pictionary-style game.” In five weeks, Draw Something has attracted more than 20m downloads which have produced some 12m active users. More impressively, according to Dan Porter, the CEO of the app’s maker, OMGPOP, Draw Something is currently generating six figures of revenue every day from advertising.

So how did OMGPOP do it?

It doesn’t hurt that celebrities like Miley Cyrus have tweeted about the game, but the real secret seems to be the fact that Draw Something requires two players, so users are naturally encouraged to introduce the app to their friends. In other words, Draw Something taps into the same viral marketing phenomena that helped propel sites like Friendster, MySpace and Facebook to mass popularity in the early days of the social networking craze. While not the first mobile app to implement viral features, Draw Something appears to be one of the most successful yet.

Not surprisingly, that reportedly has investors beating down OMGPOP’s doors. Of course, with Draw Something currently generating substantial revenue, the company doesn’t exactly need an infusion of cash.

But even if investors don’t find a taker for their money in OMGPOP, they might soon have similar opportunities if Draw Something’s popularity spurs other developers to look at ways to make mobile apps more viral.