A way to run a number of different tag queries in wordpress and then sort the results, putting the queries that match the most tags at the top.

gistfile1.php

$queries_array = {$query_1, $query_2, $query_n};

$merged_array = array_reduce($queries_array, array_merge);
$uniques = array();
$counter = array();

foreach ( $merged_array as $current ) {
  $counter[current->id] += $counter[current->id];
  $uniques[current->id] = $current; // pulls out unique only
}

arsort($counter);

foreach ( $counter as $id => $count) {
	$uniques[$id];
}