I know its nor a permanent solution but im running the following every 30 mins via cron...

Code:
<?php 

## CUSTOMIZE SETTINGS FOR YOUR SITE ##
$db_host = "localhost"; // Change this if your MySQL database host is different.
$db_name = "db name"; // Change this to the name of your database.
$db_user = "db user"; // Change this to your database username.
$db_pw = "pass"; // Change this to your database password.
$datecut = $_SERVER['REQUEST_TIME'] - (30*24*60*60);
#######################################

// Connecting to your database
mysql_connect($db_host, $db_user, $db_pw) 
OR die ("Cannot connect to your database"); 
mysql_select_db($db_name) OR die("Cannot connect to your database"); 

mysql_query("TRUNCATE TABLE `guest_info`");

# mysql_query("TRUNCATE TABLE `playlist`"); // un comment if you also don't want to track peoples entire playlists.


?>

Could should work ok, im no php expert so if there are errors I apologize but its working fine for me and speeded up the site a whole lot :D