I've said before that I hate the term Web 2.0 but that it's more than a buzzword. Perhaps what I meant to say is what Marc Andreessen said: there's no such thing as Web 2.0 (via Fred Wilson) - thing being the key word there.
The first Web 2.0 conference was held in the fall of 2004, and coincided with a large number of people in the tech industry (myself included) peeking our heads out from the fallout from the nuclear winter of 2001-2003 and realizing that the Web was not only not dead, it was thriving.
From there, it was easy to conclude that "Web 2.0" was a thing, a noun, something to which you could refer to explain a new generation of Web services and Web companies.
Many people have since pointed out that there is no clear definition of Web 2.0.
Tim O'Reilly, whose organization created the conference (and the term), attempted to define Web 2.0 as follows:
"Web 2.0 is the network as platform, spanning all connected devices; Web 2.0 applications are those that make the most of the intrinsic advantages of that platform: delivering software as a continually-updated service that gets better the more people use it, consuming and remixing data from multiple sources, including individual users, while providing their own data and services in a form that allows remixing by others, creating network effects through an "architecture of participation," and going beyond the page metaphor of Web 1.0 to deliver rich user experiences."
This is, believe it or not, the short definition.
Tim's a wonderful guy, a friend, and a true pioneer, but if the creator of the term can't come up with a crisper definition than that, what hope do the rest of us have?
What is really important is that barriers and limitations are being lifted. Or, as Marc puts it, "what we have seen over the last several years is the Web itself coming into its own."
But Marc makes it very clear that there's no such thing as a "Web 2.0 Company".
You can't build a company based on a trend.
Trends are obvious, and there's no startup opportunity in the obvious.
You have to build a company based on a new kind of product (or service -- I am using the terms interchangeably) and you have to take that product to a market.
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.
I just saw a job posting for "a product manager for a Web 2.0 (Web 3.0) product". Don't worry about whether you're a Web 2.0 or Web 2.5 or Web 3.0 company - take Marc's advice and worry about whether your product is compelling.