ApplicationPool Identity DCOM Local Activation

I have a distributed web application that has the following configuration

Web application deployed on IIS6, Win 2K3 Web Edition SP1 on the DMZ

Web application remotes to objects hosted within IIS6, win 2K3 Web edition
SP1 on LAN

Remoting is configured as follows
Server activated, single call, Binary over HTTP

Remoting on the App server runs under a custom application pool with the
following configuration
All defaults except identity. Application pool identity is a domain user
say user@domain.com.
Domain account is used to connect to SQL server using integrated security.
user@domain.com is a member of the local IIS_WPG Group

Problem: Every 29 hours (default application pool recycle time 1740 mins) I
get the following DCOM error

Event Type: Error
Event Source: DCOM
Event Category: None
Event ID: 10016
Date: 24/09/2007
Time: 01:37:52
User: DOMAIN-NAME\APPLICATION POOL IDENTITY
Computer: SERVER-NAME
Description:
The application-specific permission settings do not grant Local Activation
permission for the COM Server application with CLSID
{61738644-F196-11D0-9953-00C04FD919C1}
to the user DOMAIN-NAME\APPLICATION POOL IDENTITY SID
(DOMAIN-NAME\APPLICATION POOL IDENTITY SID). This security permission can be
modified using the Component Services administrative tool.

For more information, see Help and Support Center at
http://go.microsoft.com/fwlink/events.asp.

CLSID = IIS WAMREG admin Service

My problem is that I do not understand WHY I should grant this permission.
Granting the permission fixes my problem but I'm not happy to commit the
change until I understand why I have to grant Local Activation permission to
the application pool identity. Anybody understand why I am required to grant
this permission?