In order to hide the full posts display from the new version of WordPress 3 default theme Twenty Ten, you need to click on Wp-Admin > Appearance > Editor > loop.php file and search for the following code in it.
<div class=”entry-summary”>
<?php the_excerpt(); ?>
</div><!– .entry-summary –>
<?php else : ?>
<div class=”entry-content”>
<?php the_content( __( ‘Continue reading <span class=”meta-nav”>→</span>’, ‘twentyten’ ) ); ?>
Next under this code replace the ‘<?php the_content( __( 'Continue reading <span class="meta-nav">→</span>', 'twentyten' ) ); ?>’ with ‘<?php the_excerpt(); ?>’ which will fix this issue. Make sure that you hide the full posts from the homepage of all the blogs because this is not a recommended idea for SEO of your Blog.