(I thought you were trying to say "I just had to do a simple power and home button reset (force shut down and restart) on my iPhone 4s to
stop causing the camera app to crash when activating". I think you meant to say, "I just had to do a simple power and home button reset (force power off and restart) on my iPhone 4s
because the camera app kept crashing on its activation.")
(I need work on reading as if people are talking rather than typing)
Anyhow, did you try to do a regular/proper restart? (Hold the power button down, slide to power off, and then turn on?) If you did that, and it didn't fix the Camera App, then that would be really interesting. It would mean that cutting the power, rather than a proper shut down on iOS devices, causes some more work done on restart to fix any possible corruption?