Web annotation applications for research
Writing about web page http://sharedcopy.com/
I found SharedCopy is a quick and easy way to see what a simple annotation web application would do. It gives you a bookmarklet you can drag on to your browser, which will allow you to highlight text on the web page you are studying, stick comments and discussion threads on to it, and draw shapes on it. Then remember to save your annotations and you get a URL to their hosted copy of that web page with the overlay of your annotations, which you can then share with your collaborators or contributors. And all that for free and without even having to register for a SharedCopy account!
Although it is hard to tell whether the Gibeo project is still running, the site is still up and can help you to understand the development of this kind of services. Of course there exist many other web annotation systems.
Nevertheless I will continue exploring Diigo, since it seems quite useful for the researcher. It gives the impression of a sophisticated bookmarking service that could potentially become as community social as Facebook.
Diigo just now might be useful for a collaborative project involving commentary about web pages. However, researchers may find it cannot (yet) replace other research tools like Zotero, or even CiteULike.