Microsoft and WP7 are still struggling with encodings other than en-US (US-ASCII). A great example of this is the BingMapsDirectionsTask found in the WP7 Mango API's.
Calling this task with a culture like Swedish where the decimal separator is a , (comma) character instead of a . (dot) character, will make it fail to parse latitude & longitude data. This is 2011, soon to be 2012, how can the WP7 team miss something so crucial and in my eyes, obvious use case.