When it comes to the semantic web, the general concern amongst researchers is feasability. If implemented, it would afford countless opportunities — but the path is the problem. How would we go about developing ontologies for the semantic web? And who would spend the time writing semantically accurate markup? Search doesn't seem so terrible right now, so there's no incentive.
What if, instead of waiting for an incentive on the producer's end, the users had an incentive to implement the semantic web? I propose this idea as an initial step: a collaborative bookmarking system, a la del.icio.us, allowing for semantic tagging rather than keyword tagging.
A first incarnation of semantic tagging might simply allow you to assign binary relationships in the form subject-verb-object, where subject is always the page in question. As a naive example, consider "Brain Diseases I Wish I Had". del.icio.us users have used the tags "article", "video", "science" and "psychology" (amongst other things). Semantic tags would say that it is in the form of an article, addresses science and psychology, and contains video.
Users would contribute this information because it would allow them to search their own bookmarks easily and find new links contributed by other users more efficiently. Using current web technologies like Ajax to reccomend words for relational tags (like "contains") would help hone the network. Clustering algorithms already implemented on sites like Flickr could help answer questions about the architecture of the web and increase the accuracy of search results despite multiple naming conventions. Simple analysis would allow automated summaries of a site's contents.
Over time, more detailed semantic information could be added (like recognizing psychology as a type of science), or even imported from Wikipedia or other open categorization systems and expanded upon.