As a developer that started learning Silverlight and later abandoning it (mostly for technical reasons in that Silverlight forces you to use an ascyronous model leading to racing conditions and UI insanity).

In any case I got out early enough that I didn't get burned by MS Silverlight Gingerbread House. I do still feel a bit like Hansel and Gretel.

If you truly have super users that are "not stupid" and can craft a SQL statement then create a view of the tables specific to their login and the data they need to see and set the permissions to SELECT only for the view (Disallow UPDATE, INSERT, etc.). The problem then will be customers who think that since you opened up the database to SQL queries you should be their support and mentor when their dumb-@$$ queries don't return the values they expect, or have "errors".