If they go into the Steam server code and add:
if username = 'dingnuts': return 403
(Hint: You don't.)
So now you're back to "a database hosted at Valve" with extra steps.
If they go into the Steam server code and add:
How do you get your games back?(Hint: You don't.)
So now you're back to "a database hosted at Valve" with extra steps.