I don't think this is what he's talking about. Well, kind of, but from how I understand, he's talking more about the buttons used like they are in iOS's calenda

I don't think this is what he's talking about. Well, kind of, but from how I understand, he's talking more about the buttons used like they are in iOS's calendar: http://patrickmd.net/blog/wp-content/uploads/2008/10/iphone_calendar_sshot.png http://patrickmd.net/blog/wp-content/uploads/2008/10/iphone_... (the 3 buttons at the bottom center) Here you have 3 buttons, so it's easy to know which one is selected, but he's talking about when this is used for two different views ("often the choice is not between turning a specific feature on or off, but between two different view, modes or whatever"), and when the styling makes it hard to know which one is "pressed". Actually, the styling in the linked screenshot is not fantastic in that regard. If it had only two buttons, you would have to assume that the one that doesn't match the surrounding bar is the one that is not selected, but if you remove the bar, or change its color, you're out of luck.