Yep, latchkey, I think you might want to rethink the article. As others have pointed out, you're seeing JavaScript's behaviour, not jQuery's. And this:

  elem.data('foo', { 'a':1, 'b':2 });
  elem.data('foo'); // Returns the object

Is certainly more desirable than:

  elem.attr('foo', { 'a':1, 'b':2 });
  elem.attr('foo'); // Returns "[object Object]"