I was with the CEO of a recently IPO’d company right when they hit 500 employees. He said to me — “Jason — we’re not a start-up anymore. I don’t even know when employees start and leave anymore.”
So that’s one way to think of the term. Maybe > 500 employees you can’t possibly be a “startup” anymore.
I think the definition, like “cloud” or “SaaS” or even “enterprise”, has changed.
Start-up I think means (x) still in disrupter phase — even if a Unicorn — but (y) not once IPO’d.
Airbnb is bigger than Homeaway, the Airbnb 1.0. It’s disrupted as much as it’s disrupting. Probably it’s not a start-up anymore then. Ditto Uber.
Snapchat and even Dropbox I’d argue are still in the disrupting phase.