But the value in web2.0 sites spills over into the commons; ie. these sites tend to organize the internet in ways other than keywords.
Del.icio.us is a tool for storing one's bookmarks in the "cloud". I've written before that its best use is actually clipping and sharing news stories -- a sort of live repository of external content related to what you care about (ie. you and five friends agree to store all articles on the business strategy of Furbees in there).
But Del.icio.us also works as a research tool. The site's designers chose to use a logical, word-based hierarchy for their URLs (there's a better name for that?!). Ie. if your name is david11, your del.icio.us account is del.icio.us/david11.
What made Delicious (getting tired of the periods) unique when it emerged was its use of tagging. So, instead of just saving a news story or website to Delicious, you assign a few keywords (or tags) to it as well, allowing you to find this URL easily in time.
So, the spillover effect of most of the internet being tagged is that you can search for content by its tag, and with the logical URL system they use, that's as easy as:
http://del.icio.us/tag/a-word-that-describes-whatever-the-heck-you're-looking-for.
Even better, you can do a keyword search within this tag.
My last post was on Ryanair's business strategy. If you Google that, the results are annoying. Plan B is del.icio.us/tag/ryanair ... and then a keyword search for strategy (there are 11 answers, all of which are interesting).
Furthermore, I not only have 11 answers, but 11 people/accounts, each of which could lead to related ideas ... things I haven't yet thought of. Sort of like, if I like Fiest and RHCP, an algorithm predicts that I may like your cousins weird band from Wisconsin (most likely, I would hate it).
Google, you know algorithms ... get on this Delicious train!