Slack is a popular workplace messaging service worth $7.1 billion and reportedly on the verge of going public. Its founding team, including British CTO Cal Henderson, have weathered a lot of successes and failures to get Slack where it is today. That includes trying and failing with to start two gaming companies, and selling the photo site Flickr to Yahoo. Henderson said after the founders' experiences with Yahoo, Slack is committed to staying independent and says it has a strong chance against its key rival Microsoft because it's only focused on one product.