It seems that all of those apps also are intended to sync continuously even when you are not actively using them. When I want MMA to quit, I want it to quit!
There's always the tablet's power off button.
I googled the topic of whether Androids apps should have an exit button. Here is a rant from the developers of Android on the topic.
The advice is to "crawl from our hidden caves" towards "the new hotness" and not badger developers for an exit button, which has little meaning in an android context, as it is an "anti-pattern, which totally destroys the magic". I kid you not:
There is a lot of discussion elsewhere on the topic, but the general consensus seems to be any developer who bows to pressure to include an exit button hasn't done their job properly; ie. has written a bad app which doesn't properly manage resources, or isn't doing their part to help establish the new paradigm.
A less out there discussion of the background to topic is here from another Google engineer:
http://android-developers.blogspot.com. ... d-way.html
After thinking about it I'm pretty happy with the existing MMA design. It seems to me that the existing design is better than an Exit button.
1> It is better discoverable than a menu item, as Users may never need to visit the menu (many apps don't have one), but the notification shade is in general use, and is more in your face
2> Can be used in more situations; ie. when I want to stop listening to music, but I have navigated away from MMA
3> It is in tune with most other android apps AFAICS
4> An exit button is ambiguous; what does it do? Close the screen but keep the music playing, or close the screen & stop the music ... the existence of an exit button seems to suggest that I need to return back into the app to stop consuming resources when the music queue is exhausted, which isn't true