Would Emulating Private Variables Like This Be Wrong?

What do you think about emulating private variables for a class this
way?

function Something() {
var private;
Something.prototype.getPrivate = function() { return private; }
Something.prototype.setPrivate = function(newPrivate) { private =
newPrivate; }
}

var some = new Something("My private");
alert(some.getPrivate());
alert(some.setPrivate("Nyah nyah"));
alert(some.getPrivate());

That way the accessor methods instances are shared among instances of
Something. What do you think?