It's a popularly known dud. I suspect they sell email addresses or something lol, because the number of wishes granted never meets its supposed "limit". I tried that site as part of the Law of Attraction workings, and my wishes didn't come true ;)
But if you want to hope and believe, go ahead. The Universe grants our wishes in the strangest ways, so don't pass up an opportunity to make your intentions known. Just don't get your hopes up if you wish for something a bit out of the box.