[samaparicio]

I can only speak for the first two categories... but if you look at this paragraph from the article:

> You have some people who are using the product, but who are probably not paying for it. It is a new idea. Perhaps a revolutionary idea. No one else is doing it. And it works.

That last bit of "it works" is really important. It doesn't mean that it works technically, what it means is that it works for people as a solution to the problem, that there is a good product/market fit if you want to use lean startup terminology.