iPhone 4 - Power button unresponsive/stiff

Since it is out of warranty there's nothing really you can do other than the apple store.
Maybe you can to it to a phone repair shop and they may be able to quote you a better price.

 

I have the same problem, apparently it's quite common. If you're out of warranty then it's a replacement handset which will cost around £120.

If youre jailbroken then this isn't an issue, just assign an Activator function to lock the phone.

This problem will get worse btw, soon your button will be stuck down and not work at all.

 

Yeah that is a good point, you can use a jailbroken app to lock the phone instead of the physical button

 

I had this happen to me and ended up having to shell out the money to get it repaired as I didn't want to jailbreak my phone. I couldn't power off the phone without draining the battery completely. To lock the phone I had to set the lock timeout to 1 minute. Such a PITA.

 

Activator on cydia.
You can pick tons of different ways to lock the screen. Either hand gestures, volume or mute button movements, double tap or pinch certain spots etc....

 

If you dont want to jailbreak, theres an accesibility feature called Assistive Touch you can enable. It will put a semi-transparent circle on your screen that you can tab and access all the functions of the phone, including lock.

 

Mine just went out on my 4s. If the battery were to drain and the phone shuts off, how will I be able to turn it back on?

 

Plug it in to usb.