wp_favorites allows a logged in user to favorite a tag or tags and then show only posts that have that tag or a combination of those tags
WP Favorites allows your logged in users to favorite a tag, and allows them to see only posts that have that tag. They can also favorite multiple tags, and see only posts that have all those tags (or optionally any post with any of those tags). Example: You run a site about tea, iced and hot, green black and white. You tag every post green, black, or white, as well as iced or hot. Your user only likes iced green tea, so they favorite the 'iced' tag, and the 'green' tag. Then, they can see only posts pertaining to iced green tea (or optionally any post's tagged either iced or green). Users are able to favorite a tag from it's archive page.