When you put in a Windows 2008 SBS box, it puts in a password requirement once the mobile device (for example - an iphone) has an active Exchange ActiveSync connection.
You can alter that setting in Exchange Management Console under Oragnization Configuration -> Client Access -> right click on Windows ... Mobile Policy ... and unchecking require password on the password tab.
In my experience, you need to remove and re-add the account on the mobile device after making the settings change (at least on an iphone 3Gs I tested on)
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