Is it true that honey never spoils? Why?

Honey is very stable for a number of reasons. The main ones though are the low amount of water (most honey is under 18% water) and the high amount of sugar (which is a preservative). Both of these things keep things like mold and bacteria from being able to grow. Over a long period of time (and if left unsealed) the honey could absorb moisture and then ferment (the sugar would turn to alcohol) but if sealed then your honey should be fine for a long time. This PDF from the National Honey board http://www.honey.com/images/downloads/shelflife.pdf says that a shelf life of 2 years is often stated. On Chowhound I saw a discussion that said that in the UK the "best by" dates are usually 4 years out so I'm guessing that those dates have far more to do with decisions by the respective governments (i.e. laws that state a maximum best by date no matter what the food is) then the actual shelf life of honey. As the honey in your cupboard, if it's only a few months or a year old as long as it's been in a sealed container then it most likely should be fine.

In addition to the really high sugar-content, Honey has antibacterial properties; so far that some kinds of honey are used as an antibiotic on wounds.

http://www.sciencedaily.com/releases/2010/06/100630111037.htm has an article on that aspect of honey. This adds to the "no spoiling" capabilities of honey, because it will prevent any bacteria-related spoiling.

Sealed honey is good forever.. thousands of years at least. we know this from jars of honey found around the world that were sealed by ancient civilizations. It is an amazing substance.