this great article shows slacks amazing and inspirational growth story

> they prioritized user feedback and scaled up user testing to progressively larger groups

> they zeroed in on twitter and they really listened to users and implemented changes quickly

> They leveraged traditional marketing early on but extended its value with social media

> They had a magic number, which was a number that was meaningful to them and not just an industry metric

> They took their time to really build a high quality initial product.