Why does the face of the moon 'sync' with the earth? We never see the dark side of the moon. It rotates so that the same side always faces us.

I heard two (dinner party) theories on this:
1. The moon was made by smashing out a chunk of the earth, and so somehow preserved some orbital rotation from the earth 
2. The gravitational drag from the earth to the moon is lowest when the moon is in 'sync' to only show one face to the earth 

I don't trust either of these.

My question is: "Why does the face of the moon 'sync' with the earth?"
It is called "Tidal locking", or "gravitational locking" or "captured rotation". According the the Wikipedia page on "tidal locking" (check the references for sources), it is due to Earth's gravity causing a small tidal bulge on the Moon, which affects its rotation. Over time, the Moon's rotation, affect by Earth's gravity, makes it's orbital rotation synchronise with its lunar rotation.