Should flywheels on stationary trainers be replaced periodically to avoid catastrophic failures caused by fatigue?
Apparently you are not the first victim of this problem:  http://www.saferproducts.gov/ViewIncident/1237585

I suggest you should also submit an incident report to the CPSC (assuming you are in the US).  Since you were injured you may also want to talk to a personal injury lawyer.  RacerMate's website claims they offer an "indestructable build".

The manufacturer should provide guidance on the safe use and maintenance of their products.  I'm sure they are aware of this type of failure.

Update:  the currently shipping Computrainer flywheel is apparently made of copper.  That sounds like it would be less prone to shatter.