It's formula for a caste system.
As long as magic is actually powerful, what else could logically happen? Not to say that some works don't manage to glide over it without actually justifying equality between wizards and non-wizards, but that sort of balance of power doesn't really work.
Except when the wizards are in hiding. Which masquerade, as I have noticed before, has problems of its own.
Yet Another Reason why I prefer "anyone can do it, depending on talent and effort" wizardry.