Earlier quoted context omitted.
"Web 2.0" came around about 2004ish with Digg and other sites using AJAX. Or at least static content was not the defining factor. There were plenty of forums around in the late 90s with dynamic content.
Wikipedia disagrees. https://en.m.wikipedia.org/wiki/Web_2.0
Also see:
http://www.paulgraham.com/web20.html
I think everyone would agree that democracy and Ajax are elements of "Web 2.0."