Why do you favourite things on Twitter?

Why do you favourite things on Twitter? I know there’s no enforceable “correct” way to use favourites, but what makes sense?

I’ve favourited tweets to:

• “Bookmark” something to read later.
• Show support without passing the message on. (Kind of like a “like” on Facebook.)
• Show that you agree without replying.

Actually, I don’t do the first one very often any more. I figure someone might think I agree with or endorse the link when I actually haven’t even read it yet.

Do we really pay attention to each other’s favourites anyway?