You've been there: you remember you once found an article somewhere that you liked and now you desperately need to find it again. But on which social network did you mark it as your favorite? This is where Favs helps by collecting all stared, liked, favorite, etc. entries and make them searchable on your Mac.
But not only you collect such precious information, your friends do to. Therefore with Favs you can also follow their Favs and learn from it.
Some Service require some more than the login credentials e.g. you need a paid subscription for Instapaper and Pinboard, and you might need to set some data to public like on Flattr, Flickr, Twitter, Vimeo and YouTube.