Getting posts from multiple users?

First of all, I suggest don’t use query_posts.
(No one is really a WPSE user if had no read this answer).

So you can use WP_Query with author__in parameter in combination with array_keys PHP function.

$paged = get_query_var( 'paged' ) ? get_query_var( 'paged' ) : 1;    

$query = new WP_Query(
  array( 'author__in' => array_keys( $following ), 'paged' => $paged )
);

while ( $query->have_posts() ) : $query->the_post();
  // your loop here
endwhile;

wp_reset_postdata();

PS: you don’t need to open and close php tags on every line.