Allows ranking of items (photos, news articles) by many users, highlighting those items that users find interesting or useful. The most familiar use of this capability is by Amazon.com.
Allows users on the web to determine the content that is most useful and relevant to them, and display that most prominently. Example: a foundation might provide a news feed on their website that allows users to mark articles they found most useful, allowing those to rise to the top of a list.
Algorythymic/Automatic collaborative filtering:
Time Independent
No
High
Medium