Evernote is one of those "everything bucket" apps - a notebook that works on every device, syncs between them, and allows you to have an outboard memory, if you like. I'm a user and a fan. They've grown mainly through word of mouth and blogs - they haven't paid for any SEO or advertising
And their growth is astonishing in some parts of the work; there are 14 published books about Evernote in Japan! Growing rapidly in Spain - and Libin has no idea why.
How to they track their success? They do cohort analysis - assigning each user into a Cohort based on the month that they joined. People either drop Evernote within the first two months, or stay users from then on. And, then, and deeply importantly, the people moving up from the free to the paid service grows steadily month on month.
Conversion rates grow steadily over two years of use, hitting over 20% of a cohort 29 months after they joined.
Libin has been suprisingly free with facts and figures about his business - I wish more speakers did this. It'd ass so much more value.
"Starting a company is a bad way to make money," he says. "On average, it's a terrible way to make money. But if you want to save humanity from boredom or mediocrity or from the city of Paris shutting down from an inch of snow, then start a business."