But is this not security through obscurity?
In the database example, the issue as I understood it resolves to basically grabbing huge chunks of the database and discarding the bits you're not interested in, swamping it/them with irrelevant queries.
Or on an internet search or map search, starting multiple random searches with your particular search buried in there somewhere (as has been proposed previously to upset the large search engines' prediction algorithms.
I don't suggest it doesn't work, but it does seem to need either a lot of databases, or a lot of local storage, or a lot of bandwidth - possibly all three.