Jeff Jarvis writes in the context of Google Base:
Imagine if you could go to a page that lets you put in your resume or house ad or job ad and it spits out tagged XML you could put on the web anywhere to be found by anyone.
Or imagine putting tags on restaurant reviews you post on your blog so anyone could aggregate or search for, say, all the cuisine=mexican restaurants in location=chicago. Well, you dont really have to imagine that. If you agreed on the tags, you could start doing that today via Del.icio.us and Technorati.
And imagine if you could go to Google or other services e.g., Indeed and SimplyHired for jobs or Baristanet for three Jersey towns and see the tags they use so you can swarm around those tags and find and be found. Thats the openness we need.