My problem: How do you get baloo to index a folder on an external partition? - Add the whole partition? That could turn out to be very expensive if the partition is big, - blacklist all other folders on that partition? That could be really not practical if there are a lot of folders on the partition.
I come to think of it: I suppose there are circumstances wherein it should be far more practical to have an additional whitelist option when the folder you want to index is on the / partition too.
*** This bug has been marked as a duplicate of bug 352487 ***
In my opinion this is not a duplicate of bug 352487. In that bug the question is to replace the blacklist system by a whitelist system. I can see that only whitelisting can bring problems too. That is why I suggest to have AND the possibility to blacklist AND the possibility to whitelist.
The comments in bug 352487 make it clear that both lists are needed.