We're still at the beginning of a major transition in how people communicate and work together,
Slack is gratifying to work on in the same way that Flickr was. The mission is to make people's working lives simpler, more pleasant, more productive.
One of the advantages of something like Slack is that I tap on the app icon, and it's just the people at my company and just the people I work with. There's a strong boundary there which aids in comprehension. It's one less molecule of glucose in my brain to manage it all.
At my first job in the mid-to-late '90s, almost every product was from Microsoft. Everything was designed to work together - Windows for workgroups, shared M drives, etc., etc.
The useful part of Microsoft was that everything worked together.
There's a lot that's wrong with the way we work - bad habits that develop around control of information, people hoarding information as a means of preserving their own power. When you're using Slack, everyone can see what's going on because the default mode is public.
When we first started Glitch, there were four co-founders of the company. We built Flickr and worked together at Yahoo and then started Tiny Speck. We were split in Vancouver, New York, and San Francisco. So we used an old chat technology called IRC. Almost nothing went through email.