[Samsung Galaxy Nexus] cbarrick:
One thing I've noticed here is that the word APP is thrown around a lot. It strikes me as thinking of "apps" in terms of iOS. "Apps" in Android are more like software in Windows. In most of the Unix world (iOS and OS X included), we tend to think about our installed programs (Apple coined the term "app" for this in Mac OS) as single binaries. You run the binary and it executes directly on top of the kernel. One binary per process, essentially. Android was made to follow more the model of Windows. In Windows, installed software usually distributes it's own dynamic libraries rather than relying on some system wide packages and pretty often contains more than one binary. Then, often in Windows and always in Android, code is exicuted in a managed environment meaning the OS has a large amount of control of how the program uses hardware through abstraction and whatnot. When you open the program it starts a process and that process can spawn tasks (Activities in Android) but doesn't necessarily have to. Open up task manager in Windows. You might have 4 tasks but 30 processes.

Another thing is that in the Windows/Android model, killing a task does not necessarily kill the process. Look at Google's Music Manager for Windows. When you click the X to kill the window, the process stays open. Google does us the courtesy of leaving an icon in the system try and a way to kill the background process outside of the process pane of the task manage, but they don't have to. The same goes for Android.

Like Windows software, an app in Android contains many parts that I talked about in my last post. If you want to think in terms of iOS apps, then activities and services are separate apps. The code for the foreground activities and background services are defined independently. Since they are part of the same app package (apk) they can easily communicate with each other. (Actually, they don't really have to be in the same apk, but it's easier to think of it that way). The "app" you install in Android (likely) contains more than one thing that runs while an "app" in iOS only contains the equivalent of an Android activity. What I think is a problem in this discussion is that when people say APP they mean ACTIVITY, and they don't understand the difference. When you read about APPs in Settings->Apps->Running, that word refers to the entire collection of software, activities, services, content providers, whatever. The "app" in iOS terms is killed by swiping in the task manager thingy, but the whole "app" in Android terms is much more complex and much more powerful. I needs to keep running to keep the system working like it's supposed to. And you should note that there is no harm done by leaving an open process that runs a background service as long as the developer was competent and didn't design it to make an HTTP request every 30 seconds or some nonsense like that (which sadly I've seen somewhat often, but that was in the younger days of Android before education about the platform was widespread). You can rest assured that professional apps aren't killing your battery just because they have an open process.

There are almost three "levels" at which you can think about the Android platform. The lowest is that you don't care about process management, and you just use the system. Since most common users don't know anything about processes, this is how Android is used most commonly. The middle level is that you know about process, and you want to manage them. But now I want to ask why? Do you think it will improve battery life? The answer to that is quite simple: technically it will a little. But by any practical measurement, every bit of extra juice you feel is placebo. The deepest level of understanding Android has been discussed here at XDA a lot. With Android 2, Google did a lot on the low level design of Android. The correlation between the number of processes and battery drain is essentially non-existent. Why? Because common users don't think about processes. Android is designed for mass consumption, not just by geeks here at XDA. Just like with Windows, on a properly set up Android system (which the GN certainly is) you shouldn't have to think about processes. If you understand the Android platform, then you want the processes to stay open. Android kernels either use the Completely Fair Scheduler or the Brainfuck Scheduler depending on the decision of the kernel dev to determine when processes actually get CPU time. Both of these are complex algorithms that I don't claim to understand fully, but I do know that if a process doesn't need CPU time, it doesn't get it. Whether a process exists or not, it does not use CPU if it doesn't need to. So please quit worrying if the process is technically running or not. A running process does not mean it's using your CPU time (except for some negligible amount it takes for the kernel to keep up with it).

TLDNR: The question does swiping away a "task" kill the process is moot in the context of the discussion because it really doesn't matter if the process is alive or not. There is next to no difference in the way your GN will operate. Android is smarter than you. The real issues are A) the lack of education and understanding about the way Android handles apps and B) the poor design of some apps that end up wasting battery.