According to Mobile Mix Survey, conducted in May by advertising agency Millennial Media, 56% of all developers in the USA write software for Apple?s mobile platform iOS. This is almost as twice as more than Google?s Android developers. 5% goes to Nokia?s Symbian and 4% of devs work on software for RIM?s BlackBerry OS.

But there are more surprising facts unveiled in the survey.

• 9 of 10 developers write their apps for only one exclusive platform, and only the remaining one writes software for multiple operational systems.
• Apple?s iPhone is the most popular handset on Millennial Media?s network. It is followed by RIM?s BlackBerry Curve (7.92%) and Google Nexus One (3.94).
• Request for the Apple?s iPad on the company?s network grew 160% month-over-month, for Android-devices ? increased 15% in May.

Millennial Media?s data is pretty precise as the agency is the biggest after AdMob and covers with its network over 59,6 million users, which make 82% of the mobile Web, according to Nelson.