I worked at a startup that offered an unlimited option.

It's amazing how fast you go from thinking nobody could ever use that much of your service to discovering how many of your users are creatively abusing the service.

Accounts will start using your service 24/7 with their request rating coming at 95% of your rate limiter setting. They're accessing it from a diverse set of IPs. Depending on the type of service and privacy guarantees you might not be able to see exactly what they're doing, but it's clearly not the human usage pattern you intended.

At first you think you can absorb the outliers. Then they start multiplying. You suspect batches of accounts are actually other companies load-splitting their workload across several accounts to stay under your rate limits.

Then someone shows a chart of average profit or loss per user, and there's a giant island of these users deep into the loss end of the spectrum consuming dollar amounts approaching the theoretical maximum. So the policy changes. You lose those 'customers' while 90+% of your normal users are unaffected. The rest of the people might experience better performance, lower latencies, or other benefits because the service isn't being bombarded by requests all day long.

Basically every startup with high usage limits goes through this.

If you launch your service without knowing how much it costs to offer your service at the maximum rate it could be used, then this will definitely happen. Engineering directors need to require performance testing benchmarks and do the math to figure out where the ceiling is. If you happen to be "lucky" enough to scale very fast, you don't want to then bang your customer's heads repeatedly on a ceiling.

Not only startups, when OneDrive (was still SkyDrive at that point) started to offer unlimited online storage, from memory they said there was about 70 users that had over a petabyte of data each on the system.

Essentially people had all their security cameras and PVR units uploading endlessly to the cloud and Microsoft was footing the bill.

Then the 1TB limit came in to stop that.

This is why we can't have nice things.

It's nice to have an unlimited tier where there's no limit but you get your hand slapped when you go beyond reasonable. But people abuse shit like this and now lawyers have to get involved and we can't have the nice thing anymore.

Words mean things. Please don't call it "unlimited" if you limit it.