The KVC part of the runtime expects either a name or _name ivar when using valueForKey: on an object when it cant find a message to retrieve that variable. see http://developer.apple.com/documentation/Cocoa/Conceptual/KeyValueCoding/Concepts/SearchImplementation.html
If the runtime bothers to search for _name and the apple documentation mentions the _name first there might be a good reason for this. Let's take a look at some SDK classes: UINavigationBar.h this class has underscores in front of all ivars, UIView too... the list goes on. Well maybe it is that way with the new fangled iOS SDK and good ole NS* classes don't do thinges that way... wrong; they use the underscore as well in the header files.
Apple uses the underscore in private API messages as well as ivars. I can't understand why their examples do not push this behavior especially when the runtime bothers to have this so called "naming convention" hard coded into the variable search path. It would be nice to see some consistency.
Just a note, there is a strict naming scheme you have to follow to be KVC compliant; the link above helps you to conform to this to use this handy feature of the runtime.
