I knew that.......
That is a cat's way of marking his/her territory.... they have some kind of scent glands in there cheeks..... makes my wonder why Tinky rubs her face all over her litterbox when I am cleaning it I KNOW SHE DOESN'T THINK THAT I AM GOING TO TAKE IT AWAY FROM HER?!?!?!!

As to Lachesis question... my best guess is that your cats look to you as their mother.... like when they are nursing they (knead dough) on the mothers belly to help excrete the milk, and same with the suckling on the neck he probably just thinks that you are his mommy OR MAYBE YOU JUST TASTE REALLY REALLY GOOD?