I use favs/likes with IFTTT to save twitter links to other services.
I think the phrase "favorite" was to be read as "things that are my favorite" -- it was never used by the userbase as a bookmarking mechanism.
I think assuming it wasn't used as a bookmarking mechanism is being a bit shortsighted. Myself and many others in my circles used it as a bookmarking tool as well as to show support of something someone said.
It contains an interesting link you would want to read later? Pinboard can import favorited tweets and automatically store them as unread bookmarks, for example.