riddle - I have two faces, but show you one

I have two faces, but show you one.
I once had guests, but now have none.
I'm rarely bloody and seldom blue.
I'm often promised and sometimes new.

What am I?

Answer

You are:

THE MOON

I have two faces, but show you one.

The Moon has two faces in the sense that from our perspective it has a "dark side" or "far side" (which we never see) and the side which faces us - the oddity is that we have this relationship with the Moon.

I once had guests, but now have none.

This refers to the astronauts which have visited the Moon - there are currently no humans on the Moon - nor have there been for quite a while.

I'm rarely bloody and seldom blue.

This refers to the red and blue moons. These are rare phenomena c.f. "once in a blue moon"

I'm often promised and sometimes new.

The "new" moon is about the lunar cycles. Finally, one often "promises the moon" i.e. makes crazy promises.

Ideas:

Why not something about honey :D