[RaDiKal]

Looking at the source for a typical movie (I chose Eight Below at random), the trailers are presented in an embedded document via a link in the At A Glance tab. A code snippet from that tab would look like:

<div class="mdp-nav">
 	<a href="http://www.netflix.com/MovieDisplay?dmode=ATAGLANCE&lnkctr=mdp-tab-aag&n=1&movieid=70042689&trkid=189477">
<img src=http://cdn.nflximg.com/us/pages/browse/mdp/ataglance-on.gif
 		name="atAGlanceTab" border="0"
 		onmouseover="document.atAGlanceTab.src='http://cdn.nflximg.com/us/pages/browse/mdp/ataglance-on.gif'"
	 	onmouseout="document.atAGlanceTab.src='http://cdn.nflximg.com/us/pages/browse/mdp/ataglance-on.gif'"></a></div>

Note that the link (anchor) contains a movieid keyword value pair and a trkid keyword value pair. Within the at a glance subdocument is a preview link:

<div id="mainmoviepreview" >

    <div id="flashpreview" style="width:496px; margin-left:1px; display:none">
    <div id="flashpcontent">
    
    </div>
    <div style="margin:3px 10px 0px 5px; text-align:right"><a href="javascript:void(0);" onclick="playPreviewMdp(); return false;">Close Preview</a></div>
    </div>
    <script type="text/javascript">

           var fo = new FlashObject("http://screeningcdn.nflximg.com/us/flash/210.swf?movieId=30596&
bl=http%3A%2F%2Ftrailermap.netflix.com%2Fitem%2Ftrailers%2F&sid=101115974262662109151116343f375959b4e8a80c569dcad6e77e3523d&
dlid=30596", "flashpcontent", "496", "271", "8", "#B9090B");
           fo.addParam("wmode", "transparent");
        </script>

    <div id="description-content" style="padding:15px;">
        <script type="text/javascript">
        var isMovieRecommended = false;
        </script>

In this case it is a flash based embedded object ( http://screeningcdn.nflximg.com/us/flash/210.swf) that takes a movidID param of 30596 along with some other codes. Note that the 30596 also appears with dlid which might mean this is the download id which you could leverage.

If you don't have Flash ver 8, you'll notice a bit further down in function showFlashPreview that you'll get a "Flash 8 is required to play previews" instead of the actual preview.

If you look at a different movie that doesn't use flash for preview (such as Monty Python Live! which uses mediaplayer to play its preview), you'll see the same division (mainmoviepreview) but different functions and layout. Looking into this you will find:

playPreviewMdp(thisForm.value, 363136, 'true', 60030581, 'true');

which references the same magic cookie # of 363136 for the full screen link:

<a href="http://www.videodetective.net/player.asp?cmd=3&publishedid=363136&CustomerId=67272&videokbrate=300" 
target="_blank" style="font-size:10px; color:#FFFFFF">open in new window</a>

So the next step is to see if 30596 and 363136 exist as readable files and what form they take (flash specific and the mediplayer based more leveragable codec).