When you have hundreds of images it is best to use James Padolseys scrollstop event. Compate this to page where plugin is disabled or page with larger images.
<script src="jquery.scrollstop.js" type="text/javascript"></script>
<img class="lazy" data-original="img/example.jpg" width="80" height="120" alt="">
$("img.lazy").lazyload({ event: "scrollstop" });