The web is an incredible rich environment for information sources, however as a medium for a rich client experience it is woefully lacking. The current set of technologies fall into two extremes, HTML (fast, easy to program, and runs everywhere) and Java (complex to download, complex to integrate into the web, and complex to configure to run everywhere).
The rate of information growth is approaching exponential and the information about information is growing, but search engines still deliver information as single dimension lists!. The Semantic Web will be stillborn if we do not break free of HTML and deliver a common rich client environment.
The need for a rich client environment that, runs everywhere, is fast, and easy to program is holding back the next wave of innovation and more importantly delivering understanding to the users of information. There are a great many solutions out there but they are all falling short between ubiquity, easy to use and fast. This is the next big challenge for the web and the Semantic Web is DOA without it - who is up to the challenge?