I've been wondering about this. I'm not sure that swiping away an app really closes it, and I'm also not sure that the presence of an app on the recent apps/task manager list is actually open. For example, I just looked at the list of apps that are listed on my recent apps, then went to Manage Apps->Running, and they don't correlate. I then swiped away an app and then looked at the details of that app in Manage Apps, and saw that the option to Force Close was still available. Is there anyone who really knows the technical stuff behind this?