Exchange 2010 features two types of journaling, standard & premium. What is the difference between the two, which makes premium journaling to have enterprise user CALs? Well, the difference is in the way it is configured & the scope of the user base.
Standard journaling can only be applied on a per database level. This means that any database which has journaling enabled will have a copy of all messages that is sent & received by the users who has the mailboxes in that database. If you need to enable journaling for all users, you need to enable journaling on all mailbox databases.
--> The rest is on the blog :
http://www.howexchangeworks.com/2011/02/standard-vs-premium-journaling-in.html
