If you have an Android device that uses third party software that needs to stay alive at all times, it's likely that your status bar has a few notification icons that simply refuse to go away. Between my phone and my tablet I have so many such apps that if if I had them all active and on the same device, there wouldn't be any room for normal notifications. In fact, I've had to email developers and ask them to add the option to disable said notifications to be able to use some of the apps on my tablet at all, since a 7-inch 600 x 1024 tablet in portrait mode has only a single notification space in the increasingly annoying Honeycomb+ status bar.
So with that in mind it might be hard to understand why some apps have these seemingly pointless notifications.
However, there is a reason. A good reason. Android is built to automatically handle software running in the background, and if it finds itself in need of those resources, it can simply close them. It's safe to say that it can be more than just a little bit annoying to have, for example, an app made to force the orientation of the screen suddenly be closed for no reason.
Android cannot close an app that has an active notification, however, and that's why these apps display the notifications they do. I'd had apps that recommend using the notification stay alive without it, but then again both my devices are fairly top of the line, and I assume that these notifications become a lot more crucial on lower end devices where RAM is a premium. Either way, you should keep this in mind the next time you see the option to disable such a notification or you might find your background apps have been closed.