del.icio.us
* stores bookmarks online
* tag bookmarks
* shares bokmarks
flickr
* stores photos online
* tag photos
* shares photos
technorati
* tags blogs
This products let people share and tag personal goals online. They are a way to organise data online, a form of folksonomy (practice of collaborative categorization using freely chosen keywords).
Google already added a tagging feature to My Search History product. Another product that will have tags is Google Base.
Lack of precision and lack of a hierarchy for tags are issues that can be addressed using AdSense / Circa technology.
