Although the circle is animated using SMIL, the SVG DOM still provides a way to figure out exactly where it is (i.e., the current value of the cx attribute) at the time of processing the event. Every time the circle receives a mousedown event, it will be logged above.
P.S.: I'm using a mousedown event, because very few click events were getting through—the circle was moving out from under the mouse before the mouseup (and therefore click) was getting processed. If the circle is still moving too fast, increase the dur attribute, or reduce the width of the frame.