As I haven't seen anyone mention this, I will interject here. First off, I understand the want of some of you to use a task killer to kill specific task that you don't want running. My question to you is why are these task running to begin with.
If you use the back key to exit the application, the process with shut itself down. The only way a process would be running inadvertently in the background is a) its set to update itself periodically (which should be tweaked within the apps settings) or b) you use the home key to return to the home screen, which tells the OS that you want it to continue to run and will be coming back to that task soon. As far as bloatware like Skype, backup assistant, etc. If you haven't set those apps up and have never used them, then they are not "running" in the background. Androids OS has a place holder for them and is keeping them in a "ready" state in order to a) be accessed or opened quickly or b) store information (like contacts) that could be needed by other applications. In both cases these apps should either be removed from the phone if you are rooted and they are not useful to you, or be left alone so that apps that require their information can function properly.
I personally use autokiller in order to have control over how android manages my memory. I keep a lot of memory free so that if I do need to access several apps at once (think, web browsing, while listening to music while checking gmail and responding to a text) the android system doesn't hiccup trying to decide which task are important and which task need to be shutdown because there is enough free memory to handle it.
In the end task killers are band aids. If you set your phone up properly, and you don't hang on to apps that misbehave, and you back out of things when you are finished with them, there is absolutely no need for them whatsoever.
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