I am not a technology expert, so my opinion on this issue is an opinion of an user.
What is called Web 2.0 is really starting to annoying me and I am feeling this because it seems to me that Web 2.0 is starting to be build as if this was the next step and everybody should be using it in the future. I must say that the design, in some cases, is just beautiful. But it seems that was created a concept of the web and I do not think that is working out. It seems to me that the concept is all about sharing things and access things from anywhere, but i think in the first case Web 2.0 is working in a strange direction and in the second case I do not believe it is the best way.
Web applications are appearing like mushrooms! I like options, but I like real options. If I have two or more applications I can choose between them based on a function, for instance, that one of them have and the other do not. But this applications seem all alike. So I have 3 ou 4 but my choice for one of them is not really a choice because they do not have nothing really new or really diferent.
Now about the concept.
In Web applications (office, rss, calendar, etc) I work in the web and if I want I can share my documents (I can import and export to my computer, but a priori the work is done in the web)
As an user I do not feel confortable with this. Working in a server that I do not control and that I only can access with a net connection.
Besides we can ask: who has access to information that we created? How this things are treated? Can we be sure that this will not be used by other people?
It seems to me more useful (and safe) to work in an application installed in my machine and that I can publish to the web the documents I need to.
The other issue, accessing my work from anywhere, is a little bit strange to. I only can do this if I have a net connection. I think it is more usefull to get a Flash (based on Gentoo) , Slax (based on Slakware) or Damnsmall Linux and carry my OS with me 
So, I think I am missing the point of Web 2.0 and I need to ask: what is web 2.0 for?