Bricks, Masonry, Asphalt and Concrete - Bricks in chimney cracking and falling off

My chimney bricks have been cracking and falling onto the roof. It's not as bad as I make it sound, because they are only about the size of a playing card, and chips about half as this as a deck of cards. But, I realize this is a potential severe problem in the future if a don't do something about it this summer. However, there are a few places where the entire face of a brick has cracked off. Any ideas? Also, this is only happening to the top 2 ft of the chimney. The rest looks fine and strong.

Are the faces popping off of the brick, or did they use thin brick on your chimney?

Either way, it is probably a matter of water getting behind the brick through a poorly constructed chimney cap. Most are simply flaunched from the edge to the flue, and usually crack within a couple of years.

This is how a chimney cap should be built:

http://www.maconline.org/tech/design/fireplace1/chimneyd/chimneyd.html

Sounds like the chimney crown has deteriorated and moisture is getting behind. In winter moisture freezes and expands and brick and mortar can spall. A chimney professional can repair the crown and install a cap. Brick and mortar can be replaced/repaired.