I like Dan's answer, and I'd also suggest you check out: - Other social sites like Twitter and Meetups.com - Online community testing portal Ramen- https://ramen.is/ Above inviting individual people, you can give people an incentive to sharing your app within their community. i.e. Invite 5 people to unlock a level, connect your twitter to get more credits, etc.

The startup world can be full of big egos and back stabbing. But I'm happy to report, there are kind entrepreneurs too! The list here is based off of my experiences in the startup industry. The world needs more of these people: Ryan Hoover of Product Hunt. Not only is he incredibly hard working and funny, he will do anything he can to help you! I ran into him one day in SF and by chance asked him for his thoughts on the startup I was building. We ended up chatting for a long time and he dolled out some great advice. Sahil Jain of Adstage. It's so humbling to be around Sahil. You can sense his presence, but he also has such patience and wisdom. You can't help but feel inspired just by talking with him. Brienne Ghafourifar of Entefy. One of the kindest, humblest entrepreneurs I know. She defines the Entefy culture so well just by being herself. But she also knows how to bring it when the time comes. We've traded strategy on investing, product, and life. She's a great person changing the world.