As of SLK 1.7 I’ve added the ability to configure the SLK mappings at a web application level as well as at a site collection level. This allows site collections in a single web application to share the same mapping, i.e. the database and permission levels, without having to configure each site collection in turn.
If a web application has been configured, a site collection can override that by having its own mapping configured.
Note that configuring SLK for a web application will not create permission levels in the site collections within that all of its site collections. If required, you will have to script this manually.
A prime example of the use of this would be if you wanted the Assignment List Web Part (ALWP) in the learners’ My Sites. You can configure the My Site web application and the the web part will be usable in every users’ My Site. As the ALWP defaults to learner view if an SLK permission is not set, it works nicely for showing their assignments.