This has been an off and on problem for a while now, but in the last few days its become constant. Pressing the home button now takes a screenshot, with the camera sound effect and all, 80% of the time. Leading to lots of strange looks when people around me hear the camera shutter sound. I'm not convinced its a hardware problem. I dont think it is the power button, because when I reset the phone by pulling the battery out, it usually does the job of fixing it for a while. And surely if the power button was stuck in my phone would keep wanting to turn off.