On memberlist page with the stock 25 members the page loads more than 100 SQL queries (f.e. 113 for area51 board currently).
This is due to the can_receive_pm check in phpbb_show_profile() function (includes/functions_display.php) which adds 4 queries per user to determine if the user can receive PM to show "Send private message" link in user profile.
Although, for memberlist this is not used.