There is no such thing as a “space”.
There is such a thing as a market — that’s a group of people who will directly or indirectly pay money for something.
There is such a thing as a product — that’s an offering of a new kind of good or service that is brought to a market.
There is such a thing as a company — that’s an organized business entity that brings a product to a market.
But there is no such thing as a “space”.
And, as far as startups are concerned, there is no such thing as Web 2.0.
What happens when startups start getting referred to as “Web 2.0 startups” — or for that matter, “B2B startups” or “mobile startups” or “pen computing startups” — or as being in the Web 2.0/B2B/mobile/pen computing “space” — is that trends are getting mistaken for markets and products.
You can’t build a company based on a trend.
Trends are obvious, and there’s no startup opportunity in the obvious.
It frankly doesn’t really matter which trends, or design patterns, you incorporate into your product.
If the product is compelling to the market, it will succeed.
If the product is not compelling to the market, it will fail.
It’s not much more complicated than that.