Facebook sharing link is not showing a thumbnail of the images within the post?

Usually facebook share gets an image from the site to post and shows it as thumbnails.

If you press the share this on facebook link in my test page it doesn’t.

This is my test site: http://alexchen.info/taiwantalk/

This is the code:

<?php
/**
 * Template Name: Front Page
 * @package WordPress
 * @subpackage Prominent
 * @since Prominent 1.0
 */
get_header(); ?>
<div id="tagline">
    <div class="container">
    </div><!-- .container -->
</div><!-- #tagline -->
<div id="content">
    <div class="container">
        <div id="mainbar">
            <?php while ( have_posts() ) : the_post(); ?>
                <div class="content-block-2">
                    <?php the_content(); ?>
                </div>
                <a href="http://www.facebook.com/sharer.php?u=<?php the_permalink();?>&t=<?php the_title(); ?>" target="blank">Share on Facebook</a>
            <?php endwhile; ?>
            <?php /* Display navigation to next/previous pages when applicable */ ?>
            <?php if (  $wp_query->max_num_pages > 1 ) : ?>
                <?php next_posts_link( __( '&larr; Older posts', 'twentyten' ) ); ?>
                <?php previous_posts_link( __( 'Newer posts &rarr;', 'twentyten' ) ); ?>
            <?php endif; ?>
        </div><!-- #mainbar -->
    </div><!-- .container -->
</div><!-- #content-bottom -->
<?php get_footer(); ?>

EDIT:

I added all necessary meta tags and links:

<meta charset="<?php bloginfo( 'charset' ); ?>" />
<meta name="title" content="Article headline here" />
<meta name="description" content="Article summary here" />
<title><?php
    /*
     * Print the <title> tag based on what is being viewed.
     * We filter the output of wp_title() a bit -- see
     * twentyten_filter_wp_title() in functions.php.
     */
    wp_title( '|', true, 'right' );
?></title>
<link rel="profile" href="http://gmpg.org/xfn/11" />
<link rel="stylesheet" type="text/css" media="all" href="<?php bloginfo( 'stylesheet_url' ); ?>" />
<link rel="pingback" href="<?php bloginfo( 'pingback_url' ); ?>" />
<link rel="image_src" href="http://alexchen.info/taiwantalk/wp-content/uploads/2011/03/cheating.png" />

But this is the only thing that is shown:

asdasd | Taiwan Talk
http://alexchen.info/taiwantalk/2011/03/…

You may use these HTML tags and
attributes:

any suggestions?

<meta property="og:image" content="http://alexchen.info/taiwantalk/wp-content/uploads/2011/03/cheating.png" />

Visit http://developers.facebook.com/docs/reference/plugins/like/ and see “Step 2 – Get Open Graph Tags”

There’s also a lot of WP plugins out there that can help you to generate Open Graph tags.