What is Web 2.0?

words used to describe 2.0:
Open, communicative, contributive, interacting, create new content, mixing global with local, collaborate, inclusive...

O'Reily's list compairing web 1.0 and 2.0:

Web 1.0		Web 2.0
DoubleClick	-->	Google AdSense
Ofoto	-->	Flickr
Akamai	-->	BitTorrent
mp3.com	-->	Napster
Britannica Online	-->	Wikipedia
personal websites	-->	blogging
evite	-->	upcoming.org and EVDB
domain name speculation	-->	search engine optimization
page views	-->	cost per click
screen scraping	-->	web services
publishing	-->	participation
content management systems	-->	wikis
directories (taxonomy)	-->	tagging ("folksonomy")
stickiness	-->	syndication

Other definitions:

applications that facilitate interactive information sharing, interoperability, user-centered design, and collaboration on the World Wide Web. ...

dynamic and shareable content and social networking

users participate by generating their own content