You technology guys only here thinking about the technology. Web 2.0 is defined as social networking era on LinkedId, blogs, Flicker and other Web 2.0 sites.
Being involved to develop Internet since 1993 (I worked for Sience Academy) and later was involved developing lot of Internet standards like first HTML browsers for Netscape, Search Engine algorithms for Inktomi, etc we had clear goals.
We needed HTML to publish and link documents which could be immediatly available for community rather than sending printed publications.
We had news protocol (currently abandoned) to subscibe and participate in group discussions.
As the number of information started to grow, we had need to develop search engines to find proper information.
Those where the days, that we even had our own Satellite Disch to connect to the Internet as telcos where not supporting IP protocol.
But somehow between 1999-2006 everything changed. Internet was taken over by Scam Artists, SPAM, Get Quickly Rich Schemes, multinatinational telecommunication and media companies.
This generated new professions, like
SEO, SEM, Web Designer, PPC specialist, call centers for telecoms to handle huge amount of unsatisfied novice customers, etc.
Web 2.0 is just putting Internet back to his roots.