Since the target is to have nepomuk + strigi index all data, i.e. enable it by default for all folders it would be usefule if there was a simple checkbox in a folder's properties (dolphin > right-click > properties) to disable the indexing for those few folders one really does not want to have indexed. kmail does already provide such a simple checkbox which works better than having to select/deselect folders in a separate GUI. Reproducible: Always
I'm reassigning this bug against Dolphin. Dolphin can easily edit the nepomuk configuration and add a folder to the list of excludes, and nepomuk will respect that, but the important part is providing a interface for this.
If I understand correctly, this report is about the 'Properties' dialog, which is not part of Dolphin, but of kio/file in kdelibs.
There is a KCM, systemsettings -> Search, that can be used to exclude a folder from indexing. Closing, feel free to reopen if you disagree.