Applications for annotating websites and adding interactivity to the web have been around for a while (e.g. Fleck, and Dispute Finder) without really catching on, but that may change now that Google has introduced Sidewiki. The feature is an addon for the "enhanced" Google toolbar; as Google will tell you, "For enhanced Toolbar features to work, Toolbar has to tell us what site you're visiting by sending Google the URL." That might be a privacy issue for some people. Sidewiki, PageRank, and future page-related services are all part of the enhanced Toolbar. Also, Sidewiki reportedly does not work in Google's own Chrome browser (!) Jeff Jarvis makes the interesting point that "Google is trying to take interactivity away from the source and centralize it", and - for a clear explanation of what Sidewiki is all about - I find Philip Lenssen at Blogoscoped is more informative than Google's own learn more page. It will be interesting to see how this develops; will it be a useful feature, or will it merely generate even more worthless noise? Two years ago, Google introduced commenting on its news site, but only for a special subset of readers: those people or organizations who were actual participants in the story in question.(that feature never made much of a splash, and I can find no longer find any trace of it at the news.google.com.) Now, in the Web2.0 spirit, everyone is being invited to add their 2 cents.