How to sell an app that goes viral, according to $3.8 billion Slack's marketing chief

Salesforce There's no question the work messaging app Slack is one of the most viral business apps of all time. In a little over two years, Slack's worth has gone from zero to $3.8 billion, adding 3 million daily active users, 930,000 paid customers, and over 500 employees — mostly based on word-of-mouth. That's pretty crazy growth even by Silicon Valley's lofty standards. Even Slack CEO Stewart Butterfield once admitted he has "no f—king idea" why his app is so popular. But Slack's ke...