Rules are made to be broken, right?
On cache
There's an Android API which allows any application to access a reserved directory for temporary files, such as application and cache files.
The developer manual has this to say on the cache topic:
...you should always have a reasonable maximum, such as 1 MB, for the amount of space you consume with cache files...
Yet most applications routinely exceed that amount. Currently on my very own phone:
Browser: 4.84MB Market: 1.92MB TweetDeck: 21.71MB Google I/O 2011: 3.77MB GMail: 3.10MB StreetView: 2.38MB
... etc
TweetDeck is maybe the eye-catching one (hey TweetDeckers, what about deleting old cached avatars once in a while!?) but undoubtedly the really outrageous ones are the very apps that Google is producing.
Now, with phones getting more space maybe it's just common sense to update the developer manual, and place the soft-limit in something more than 1 Megabyte. Meanwhile, seeing these infractions being blatantly committed seems just like a license for doing the same without any guilt.
On lights out
On their "Honeycomb highlights" Google I/O session, Romain Guy and Chet Haase stressed that the Android system bar was "always on", to allow people to move around. It contains the software buttons for HOME, BACK, etc, that tablets do not present in physical form (unlike Android phones).
Games and videos should use the "lights out" mode, that allows applications to "dim" the contents of the system bar, hiding most of the content on it and just leaving three subtle points on screen which actually perform the functions of the HOME, BACK and TASK SWITCHER buttons, but are subtle enough to avoid attracting your attention to them instead of focusing on the application. So it's sort of an emergency light leading to the exit door. And it mostly makes sense...
Yet the camera app in the Samsung Galaxy Tab that was generously given to attendees doesn't follow this rule at all. It totally fills all the space in the screen... and adds a back button to its own interface. Instead of lights out, this is lights out, bulbs removed from the lampholder, and a small custom lantern for finding your way out.
On orientation
Another topic that caught my attention in that same session was the stress over orientation, and more specifically, forced orientation. As in when the developer assumes that the user will obviously want to use a device in an specific orientation, and locks the app to use that one and only.
Yet the Market app in the Galaxy Tab forces you to use it in landscape, whereas I want to use it in portrait!