Limiting Admin Backend Search to Title

This is possible by altering the search query via the posts_search hook.

http://core.trac.wordpress.org/browser/tags/3.3.1/wp-includes/query.php#L2202

A default search query will look like this:

..AND (((wp_posts.post_title LIKE \'%search terms%\') OR (wp_posts.post_content LIKE \'%search terms%\')))

We need to remove the post content search, a regular expression should be enough.

add_filter( 'posts_search', 'wpse_45153_filter_search', null, 2 );
function wpse_45153_filter_search( $search, $a_wp_query ) {
    if ( !is_admin() ) return $search; // work only in the dashboard

    $search = preg_replace( "# OR \(.*posts\.post_content LIKE \\'%.*%\\'\)#", "", $search );

    return $search;
}

Note that the regular expression has not been thoroughly tested and may have edge cases when other plugins or themes alter hook into here.