You might want to ask whether users have installed any game associated with OpenFeint. Some examples are listed on their Wikipedia page: http://en.wikipedia.org/wiki/OpenFeint.
Heh, I've been compiling the same list as you already did. My results look a lot like yours.
What do you mean that it is "very dangerous"?
As I posted in another thread... I wonder if it is significant that so many of the UDIDs are known to OpenFeint. If you took a random sample of UDIDs, how many would OpenFeint have data on?
