"Take a look at Pinterest’s one-year traffic on Compete from Oct 2010 to Oct 2011, which is the picture in this post, and shows Pinterest rising from 40,000 to 3.2 million monthly unique visitors."

"interpolated the curve using constant growth and put the results in this Google Spreadsheet."

"But what if every user only refers, say 0.2 new users? Contrary to popular belief, this can also lead to a sustainable business."

"However, the lack of pure virality implies that you absolutely must retain existing users to grow. This is why daily active users and monthly active users are such important metrics, and are tracked maniacally by CEOs and investors."

"Many startups are pushing way too prematurely on press before they’ve demonstrated real sustainability."

"Pinterest’s story is much different – they didn’t have the same early “hype spikes” as many other startups do, standing at only 40K uniques 8 months after launch!"

"It took Pinterest quite a while for a network-effect to take hold."

"But if it doesn’t exist initially, you must work to perfect a soft onboarding of virality that’s based on high engagement, and create a product that people love and will come back to, while layering viral techniques on top of that."

"And I’m sure Pinterest made a bunch of product tweaks early on to iterate around sharing and engagement, as virality took hold."

"Then when a user is ready to pin content, they create an account and go wild – Pinterest leverages web content from Tumblr like no site that has ever existed, thus riding on top of its network-effect while not requiring user generated content like many services."

"They’ve also perfected in-network virality (pin, repin, like) in addition to out of network sharing (Facebook, Twitter) to grow virally."

"For these reasons Pinterest could conceivably grow as fast as any consumer service we have seen in recent memory."