I have an iPhone 4 and don't recall reports of the power button failing. I tend to think their might have been a batch of devices affected, but not enough to warrant a massive recall. Lawyers will always file lawsuits in order to get rich and the consumer would be lucky to get a $5 credit for iTunes in this case if the lawsuit is successful. Complete waste of time and resources.
A lawsuit has been brought against for selling iphone with faulty power buttons.
It is said that Apple knows this issue and failed to fix it. And the power buttons of iphone 4 often broken shortly after 1 year warranty. And the iphone users need pay $149.99 replacement fee.