http://mashable.com/2012/06/15/why-p...attery-drains/

A team of researchers at Purdue University released a study to TechNewsDaily that thoroughly examines what dozens of popular apps are doing on Android phones, and what many of them are doing wrong. (Though the study was only on Google’s Android operating system, the researchers say that they can do the same for Apple’s iOS and Microsoft’s Windows phone operating systems.)

Apps turn on parts of the phone, such as the processor, the GPS or the camera, when they need them, which is normal. But by digging into the code of apps, the researchers often found what they call “no-sleep energy bugs,” mistakes in the program that fail to turn the components off when they are done. Unlike computers, which are often plugged in and “awake” most of the time, smartphones try whenever possible to be in a “sleep” mode to save precious battery life. But buggy apps defeat the purpose. [How to Improve Android Smartphone Battery Life]

The apps you download aren’t the only culprits — many that are part of the Android operating system are overtaxing the hardware. Culprits include the native email program, Google Maps, the Android backup service and, ironically, the power manager that is meant to conserve battery life. The preinstalled Facebook app also overuses the phone’s battery. Most of these problem apps, the Purdue researchers say, were previously unknown.
I bet fixing these bugs is a pretty low priority for the companies, too, as all that happens is increased power consumption, which most phone owners probably don't even realize is happening or why.