Not a developer, so bear with me. To what extent are developers allowed to focus on power efficiency in the applications they develop? From what I can tell, there are so many other more pressing business considerations that power savings must get pushed pretty far down the list.
Depends on the type of app you are writing. Take a developer writing a game where he has control over all aspects of the app. He or She could take various steps to reduce energy intense operations such as using wifi, bluetooth, 3G etc. Keeping that to a minimum will help prolong battery life. But if you are writing a business app with little freedom to spend time on managing that stuff effectively then that can cause poor results. The ability to reduce power consumption is there but not everyone takes the time to do it. Take a look at this video for more info on it.