The term, Library 2.0, is most certainly a contested one. Just have a look at the opposing views of The Annoyed Librarian and Meredith's blog to compare - although AL can be seen as a "tongue-in-cheek" protester, those views are critical to the way we think about the evolving library service.
The definition, as well as implementation of these evolving technologies, are at the heart of what constitutes librarianship today. I would say.
I won't be going into the definition debate in too much detail in my research - the definition dialogue warrants a research paper in itself.
I will however include it in my literature review as it has everything to do with how and what people think about the Library 2.0
Maness (2006) has attempted to define what we actually mean by Library 2.0 and more recently, Habib (2006, pdf) proposed a definition, based upon Maness' and others work, but in that proposal Habib readily acknowledged that the term was contested and is under constant criticism.
Habib's definition is based upon the coined concept of ‘Web‘ and '2.0' which he points out is preceded by the concept of 'Business 2.0'. The synchronising technology, marked by the 2.0, and points to the radical changes that have occurred in the past 2-3 years as people attempt to utilize it for whatever purposes, be it businesses, web commerce and communication and, as I'm attempting to explore, in libraries.
O'Reilly's definition first set out to disseminate the chaos of the web in terms of how changing technologies defined those that survived the first internet crash. In essence that explains what 2.0 stands for. It's a generational mark, for technological innovation.
Habib's definition is very diplomatic - it's levelled, in a sense. It disregards the hype surrounding the term and manages to imply the impact the new technologies can have on a library service without excluding more traditional services.
This defintion debate seems to be going on strong. For now, at least. Which is good.