Tagging is quietly but massively disruptive. The fact that thousands of webmasters and bloggers tag their content so that they can be found by Google is Google's secret weapon. But it could get turned against them. A small incentive to be found by other search engines will change tagging behavior. This is likely to play out in lots of vertical niches, where a small change in tagging behavior can make a huge difference in findability and that can make a big difference to both buyers and sellers. Whether people use RDF or Microformats or some other defacto vertical standard will continue to be the subject of much debate, but the format itself is not the issue. The human drive to tag (to order one's world) is deep and strong and has financial motivations as well.