Not always. You have to be careful. If left alone the rodent can actually harm or kill the snake. A friend left a feeder in with his ball python after it didn't eat it. He came back after a weekend away and the mouse had bitten the snake in several places including its face. It was lucky it didn't lose an eye. The snake still didn't kill the mouse.
"Do you have to live so relentlessly in the real world?"
-To borrow the words of Bill Watterson.
Just found the link. Looks like it is a mashup of this post and another one. Or this post and the other only show parts of the story. Interesting discussion in the comments though.