Hello,
Since the logging folder is merely a location on the server where IIS will create and store the log files for the site in question, you are completely safe to not assign permissions for the 'IIS_WPG' group. Also, any programs that you have which process web site statistics will need to be pointed this folder to generate statistics from the log files.
Hope this helps! : )
Jonathan K.
Technical Support Representative
http://www.ServerIntellect.com
Managed Servers, 24x7 U.S. Support, Web Hosting Solutions.