Slack's big new thing is called “Shared Channels”. They “work just like the Slack channels you’re used to using with your internal teams, but connect two separate organizations, giving both sides a shared space to work together and move projects forward.” Slack admins in each organisation retain rights to add their own users to the Channels, or not.
Sounds good, eh? And doubtless it also sounded good in the mid-1990s when Lotus/IBM/Notes/Domino allowed shared databases and applications that could include users from across different organisations. In those far-off days your correspondent worked with clients who insisted on that arrangement, deeming emails a blunt instrument and forcing us to acquire some Notes licences that IT really wasn't very keen on.
Not many years later, vendors who caught the Intranet bug took things a step further by cottoning on to the idea of an “Extranet” that could be accessed by third parties outside the firewall. That idea was even layered on top of SharePoint a decade ago.
Slack probably doesn't care that it's not entirely original, because its business is built on taking collaboration ideas that never evolved and making them more usable. The company's core group chat functionality has been around for decades but never evolved to take advantage of modern PCs' powers, or made it easy to play with images and links.
If Slack can make shared spaces more usable than its predecessors, good luck to it. But don't mistake Shared Channels as innovative. And don't forget to think about security: Slack says “channel members from both sides can … upload files”, a use case for data leak prevention tools if ever we heard of one.
Shared Channels will only be available to users of Slack's paid plans. The rest of us will have to make do with vanilla Slack teams, as they already allow users from different organisations to mingle. Such teams and the channels they include do not, however, match Shared Channels' trick of appearing in a single list of Slack Channels. ®