Adding scaledSize to the image/icon and optimized: false to the marker solved it for me.

http://jsfiddle.net/kQRbr/31/

var image = {
    url: 'https://cdnjs.cloudflare.com/ajax/libs/foundicons/3.0.0/svgs/fi-marker.svg',
    scaledSize: new google.maps.Size(100, 100),
}

var marker = new google.maps.Marker({
    position: sanfrancisco,
    map: map,
    optimized: false,
    icon: image
});