Excellent article. For me, email is still the killer app. I was an exec in a 5,000 person company, and in the 80’s we started using MCI mail, and pretty soon we were basically running the company on email. It was a tool that bound together our far flung offices, and it flattened out the org chart allowing anyone to contact anyone in the company. You might never have talked to the CEO, but now, you could just send them an email. The Internet was a huge boon to email, helping consolidate the private services like MCI mail. Now you could contact almost anyone. I have a number of email accounts, but they all feed into my primary email account… the ability to search through all of my conversations in one place has dramatically improved my productivity. Having messaging fragmented by things like Slack destroys the single point of contact and searching. I am on several Slack channels, but I almost always email my colleagues instead. Email has issues but nothing else comes close in terms of value, productivity, ease of use, and connectivity.