“Try this experiment in Mac OS X 10.7 Lion. Start up TextEdit. Close any open document windows. You’ll notice, from the name of the application appearing next to the Apple menu, that TextEdit is still running (it isn’t one of those applications, like System Preferences, that quits automatically when its last window closes). Now switch away from TextEdit and do something else for a while. Then use the Command-Tab application switcher to switch back to TextEdit. You can’t. It’s gone. You weren’t actively doing anything with TextEdit — it had no open windows and it wasn’t the frontmost application — so the system quietly told TextEdit to quit. Worse, if TextEdit appears in your Dock only when it’s running and this happens, its Dock icon mystifyingly disappears.”
This is what I was afraid of! I like to drive not the computer. Please Apple, let me turn this off, at the VERY least leave it in the Dock/CMD+Tab.