Slack

Slack, now a fixture of how companies talk to each other, was never meant to be a product at all. Stewart Butterfield and his team at Tiny Speck were pouring themselves into a strange, ambitious browser game called Glitch — and it was failing. By late 2012 they shut it down. But along the way they'd quietly built something to coordinate their own distributed team: a chat tool with file sharing and searchable history that did what email and IRC couldn't.

For founders and operators, this case is a prompt to look sideways at what you're inadvertently inventing while doing the real work. The scaffolding, the internal workaround, the integration hack — any of it can outvalue the main thing on the roadmap, because a problem that hurts you enough to solve probably hurts others too. It sharpens attention on the internal tool outsiders keep asking about, and what it would take to recognize the byproduct as the real business.