Two years ago, we were debating whether Microsoft should buy Slack to gain credibility in the emerging market for chat-based collaboration. But the software giant went in a different direction, and it announced it would develop its own product, Microsoft Teams.

Today, it's clear that the software giant made the right decision. But that wasn't always so clear. In fact, Microsoft was considering acquiring Slack in early 2016 for about $8 billion. But Microsoft CEO Satya Nadella and co-founder Bill Gates both believed that Microsoft could build a Slack competitor based on Skype for Business. And so it did.