To me once you have revenues of 1mm per year, you are no longer a startup.
I was wondering about the definition of "startup" the other day. Would it be reasonable to define it in terms of profitability? Once you reach profitability you have a proper, self-sustaining business; before that you're in the much riskier position of being a start-up, burning through cash in the hopes of becoming profitable later on. This would mean that things like restaurants fall into the startup category only briefly, while (say) biotech companies can be startups for a decade or more.
You can have all the funding in the world, or have been operating for 10+ years, and it still may not be clear that you've got a viable business.
I do think it's important to distinguish between startups and growth companies. Facebook is no longer a startup, it clearly (to me at least -- though I'm sure this will be contentious) is a viable business, all that extra VC is about fueling mega-growth.
If it's not a "start-up", what is it? It sure as hell isn't an "established, profitable business." It's not established because people are still willing to invest 100s of millions of dollars based on a hope that it'll pay off huge later and it's obviously not very profitable.