15. A computer system that allows a first user to view a collaboratively annotated electronic document, the computer system comprising: a memory; a processor; a friend-list-generating mechanism configured to generate a friend list comprising a plurality of friends based on similarities of web browsing behavior between the friends and the first user; a ranking mechanism configured to rank the friends based on degrees of the similarities between these friends and the first user; a monitoring mechanism configured to monitor the friends' web browsing behavior; an identification mechanism configured to identify an electronic document associated with the monitored web browsing behavior of the friends; a retrieval mechanism configured to retrieve the identified electronic document; a determination mechanism configured to determine whether at least one of the friends has annotated the electronic document; an augmentation mechanism configured to augment the electronic document using annotations from the at least one of the friends, wherein while augmenting the electronic document, the augmentation mechanism is configured to: highlight at least one portion of the electronic document; and insert a tag field that indicates a tag word chosen by a friend associated with the highlighted portion; and a display mechanism configured to display the augmented electronic document to the first user.
15. A computer system that allows a first user to view a collaboratively annotated electronic document, the computer system comprising: a memory; a processor; a friend-list-generating mechanism configured to generate a friend list comprising a plurality of friends based on similarities of web browsing behavior between the friends and the first user; a ranking mechanism configured to rank the friends based on degrees of the similarities between these friends and the first user; a monitoring mechanism configured to monitor the friends' web browsing behavior; an identification mechanism configured to identify an electronic document associated with the monitored web browsing behavior of the friends; a retrieval mechanism configured to retrieve the identified electronic document; a determination mechanism configured to determine whether at least one of the friends has annotated the electronic document; an augmentation mechanism configured to augment the electronic document using annotations from the at least one of the friends, wherein while augmenting the electronic document, the augmentation mechanism is configured to: highlight at least one portion of the electronic document; and insert a tag field that indicates a tag word chosen by a friend associated with the highlighted portion; and a display mechanism configured to display the augmented electronic document to the first user. 16. The computer system of claim 15 , further comprising: a notification mechanism configured to notify the first user when at least one friend has annotated an electronic document.