The shake lights are great as a demonstration of a scientific principle, but as a flashlight, they are a joke.
I have several crank lights...
There are numorous posts on CPF by owners of high quality shakelights who express their satisfaction with them. Note that the
NightStar in the review I linked to above actually has a street price of ~$40. The joke is on people who insist on buying their shakelights at the Dollar Store.
I would definately put crank lights into the joke catagory in ANY sandy, dusty desert environments AND in any marine locale with salt water and salt air. In both of those situations one may stow a
well made shakelight and just forget about it until it's needed years later. When you finally bust it out when you need it chances are that it will work the same as it did when you first laid it away. The same can not be said of ANY crank light. The fact that they are so well sealed against the elements is ONE of the shakelight's
greatest appeals.
Crank lights, on the other hand,
are impossible to seal against sand, dust, salt air and salt water. Even if one was sealed up in a container that protected it from those environmental factors, once you break it out in an emergency under those conditions it's days will be numbered.
As far as being
a true emergency light that will stand up in many of the challenging environments where many people may really need them, I don't think crank lights have anywhere near the endurance required. For many difficult environs I'd go so far as to say that the name of these lights is a better discription of the designers than of the light itself.