Here is the test:

test("Use prototype method as event handler", function(){
	var $elem = $('#swipeTarget'),
		SomeConstructor = function($elem) {
			$elem.bind('test', this, this.handler);
		};
		
	SomeConstructor.prototype = {
		handler: function() {
                        var that = event.data;
                        ok(true, "Called.");}
	};
	
	expect(2);
	obj1 = new SomeConstructor($elem);
	obj2 = new SomeConstructor($elem);
	$elem.trigger('test');
});

The test will fail. Only obj2.handler will be called.

jQuery tracks event handler (for unbind) by adding them an unique guid property, and only one guid / element / event can be registered. In this case obj1.handler and obj2.handler are the same function and share the same guid.