I'm having trouble coming up with a scenario, other than taking advantage of ownership chaining, where I would want to change the ownership of an object, like a table, so that a user different than the schema owner owns that object.
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For example, in AdventureWorks, dbo owns the HumanResources schema, which contains a table called Department. dbo implicitly owns the Department table because it is contained in the HumanResources schema. Using ALTER AUTHORIZATION I can change ownership of the HumanResources.Department table to a different user, testuser.
And if such a scenario does exist, wouldn't GRANT CONTROL be a viable alternative to changing ownership?