my understanding of shake is that it is caused by wind damage- the wind blows the tree around and the rings are too brittle to hang together.
Any time i've seen shake and then tried to use the log i've always been dissapointed-even when there is very little shake present to the eye the wood quality always seems poor.
on the other hand i have never seen shake develop after a log is cut....just checking,warping,bowing,end splitting,rotting, bug infestations, mold, case hardening, etc, etc.
-Mark in Ontario.