Decided to write an article about task killer use, mainly because of so many people being surprised that i do not recommend it, after their so called techy friends told them they need one, I'll post the opening paragraph with a link to the rest of it.
Android Guide: Should I Use a Task Killer - Droid Den
Task killer, one of the most prominent words within the android world. One that causes many arguments and confusion, well today lets see if we can put it all to rest.
I am constantly surprised when talking to new android owners that come to me with questions about their "faulty" phone and "poor-performing" battery, to discover that one of the first apps they installed was a task killer. Even more surprised when I dig deeper and ask why, with one of the top responses being because their "techy" friend said its a vital app. First things first, anything vital will be a core part of the the operating system. If google required that a task killer be a core part of their os, they would have included an easy way to kill apps, end of. Also, if your "techy" friend told you to download an task killer, please, ignore any advice from them in the future, you will regret it if you don't.
Android Guide: Should I Use a Task Killer - Droid Den