"Is sloppiness in speech caused by ignorance or apathy? I don't know and I don't care." -- William Safire
With its allusion to the version numbers that usually designate software upgrades, "Web 2.0" was a trendy way to indicate an "improved form" of the World Wide Web, and the term has been in occasional use for several years. It was eventually popularized by O'Reilly Media and MediaLive International for a conference they hosted after Dale Doughery mentioned it during a brainstorming session. The participants assembled examples — "DoubleClick was Web 1.0; Google AdSense is Web 2.0. Ofoto is Web 1.0; Flickr is Web 2.0" — rather than definitions.
An earlier usage of the phrase Web 2.0 was as a synonym for "Semantic Web", and the two concepts complement each other to some extent.
Web 2.0 has since come to refer to what is described as a second phase of architecture and application development for the World Wide Web. Web 2.0 applications use a combination of techniques devised in the late 1990s, including public web service APIs (from 1998), AJAX (Remote Scripting) (1998), and web syndication (1997). They often allow for mass publishing / sharing (web-based social software). I've already run out of both fingers and toes for counting those. The term may include blogs and wikis. To a large extent Web 2.0 has become a buzzword, and there is no shortage of derisive blog posts and articles about this. I suppose you could consider this another of them.
Many of the ideas of Web 2.0 have been employed on websites that were around well before the term was developed. Amazon.com has allowed users to write reviews and consumer guides since its inception -- a form of self-publishing -- and opened up its API to outside developers in 2002. By Internet standards, that's ancient history. When a website proclaims itself "Web 2.0" for the use of some trivial feature such as blogs or gradient boxes, it is generally more of an attempt at self-promotion than an actual endorsement of the ideas behind Web 2.0. It has been reduced to a marketing buzzword, like 'REVOLUTIONARY', that can mean whatever a marketing person wants it to, with little connection to most of the good ideas that it is supposedly based on. It could also be argued that "Web 2.0" does not represent a new version of World Wide Web at all, and is in fact comprised entirely of "Web 1.0" technologies and concepts. Basically, it's still HTTP, which is by now prehistoric. If I give my Model T a spanking new paint job and hood ornament, it isn't likely to pull my 65 foot boat trailer up the hill any better.
I mean, let's get with the program here -- if I truly have developed something advanced and new, shouldn't I brand it "Web 3.0", or perhaps, "Web 10", just so that people are sure not to get confused?
Other criticism has included the term "a second bubble" stating that there are too many Web 2.0 companies attempting to create the same product with a lack of business models. There is already significant evidence with some recent IPO's and VC$$ deals that we may have already completely forgotten the dot-com bubble of 2000 and are willing, once again, to throw good investment money down the "Internet toilet", at some of these "Web 2.0 vapor-ventures", so to speak. The whole thing just makes me want to press the "Fart button". Is GOOG a good buy at $337? Was it a good buy at $475? I bet a lot of investors are having second thoughts about that purchase. Hey, it's only selling at 67 times earnings, can't you take a joke?
My Advice? If you see "Web 2.0" anywhere, unless there is significant content and value that is immediately visible, accompanied by a mature absence of hype, run the other way as fast as you can.