Exclude All Posts Which Do Not Have A Tag Assigned

here is an example loop..
you can change the number of tag to exclude based on the amount you want…

<?php 
if (have_posts()) : while (have_posts()) : the_post();

// GET THE TAGS OF CURRENT POST IN LOOP AND COUNT THE AMOUNT
    $posttags = get_the_tags();
    $howmany = count($posttags);
    if($howmany > 2) {
?>
    <h3><?php the_title(); ?></h3>
    <?php the_excerpt(); ?>

<?php
    } else {
    // do nothing
    }
    endwhile; 
?>
<?php endif; ?>

.

Hope This Helps
Sagive