Normally I use Danish as the iphone language. When I use some apps written in English, something tells voiceover to switch the synthesizer language back into Danish, maybe when a new page of the app is opened, or in the case of Twiterific as soon as I touch an area in the status bar.
When you have more than one language installed in VO you see the languages in the rotor, but also what VO calls the standard language, and often this is what Vo decides that I want to use.
With the synthesizers in iOS it is very anoying to have a missmatch between UI language and the language used by the synthesizer.
Since this only happens in some apps, there must be a way to tell Voiceover not to use the default language. Of course one solution would be app specific VO settings, but this idea does not seem to be what Apple accessibility is working on.