It sounds like more of an engineering issue. I'd imagine that unlimited-up-to-the-capacity-our-system-can-handle is reasonable.

The biggest takeaway from this should be: if you think you might be pushing a system, you should probably talk to a human first to get confirmation on how it will work for your specific scenario, and not just use their sales page.

Particularly when that tool is so important to your operations.

It might if they were paying for 10000 users but only some power of 2 less than 10000 could actually sign up. And Slack refused to refund the difference.

False advertising regulations aren't a company destroying "gotcha" like felony theft, they are designed to protect consumers from fraud. Having some technical issue that doesn't impact the vast majority of consumers isn't what it's designed for.

It kind of reminds me of cell network "unlimited data" where they just start aggressively throttling customers after a certain amount of data use.

Not if the "customer" paid $0. If I give you something for free, you have no recourse if I didn't describe it to you properly.

To be fair to slack, the quote is "there's no limit to the amount of people you can add to your team". They're saying that as you team grows, there's no limit.

Not students or subscribers. Not "public channel", or "chat room", or some sort of phrase that indicates a large mass of people.

If someone decided to sue them or something, I'd assume they'd have an easy defence saying they clearly meant a team of work colleagues. As many others are saying here, slack simply doesn't seem to be aimed at this use case.