About 10 years ago I did a spoof version of a 50 Cent song and posted it on one forum - it took off in a really big way with people sharing it on forums and via email (this was before YouTube or Facebook), and ended up getting heavy radio play all over Europe and Australia. I signed a management and publishing deal and ended up producing music professionally for a few years before I decided to go to college for computer science.
The power of creating something resonant and putting it on the internet is huge, and it's still totally possible today.
I believe that consumer startups in the early stages are no different. You need to find a way of presenting yourself that resonates emotionally with your desired audience, to the extent that they want to share that feeling with others.
Congrats on the viral success! It's a really fun experience.