Well good news for all AT&T users as now you can also install 3rd party apps on device and Samsung Infuse 4G will be first phone to allow sideloading apps. AT&T users have long been denied the ability to install applications 3rd party apps on the Android Market on their device, but these strict restriction may soon be lifted.
Source: Sideloading Apps Now Allowed on AT&T With Samsung Infuse 4G
Source: Sideloading Apps Now Allowed on AT&T With Samsung Infuse 4G