Hint: you have to uncheck two checkboxes that OS X explicitly tells you about in the very same Spotlight preferences, plus another one in Location preferences.
What I meant with explicit was that they are explicitly described in the text that is shown on clicking the button called "About Spotlight Suggestions and Privacy."
If one would never even open Spotlight preferences, then yeah, it is not possible to see, enable or disable those preferences. But then one should also not complain that it is impossible to enable or disable these preferences. By that logic, every application that does anything with any privacy implications should have it's primary interface littered with preference toggles to make it completely obvious how it's functionality can be altered.
I think a basic warning, information or other type of system making a user aware, that all their searches are being shared with 3rd parties is not an unreasonable demand.
Having people go to two preferences dialogs just to find out that contents of search box are being sent to USA datacenters is a dangerous dark pattern.
