Let's say your iPhone was running low on juice. Normally, you might tweak multiple settings separately. But with a smarter Siri, you could say "Save my battery life" and iOS would automatically tweak multiple settings, such as lowering the brightness and turning off Bluetooth and perhaps Location.
Here's another example. "I'm in a meeting. Only let Honey through." Siri will automatically mute the ringer and not even buzz your pocket unless your wife calls. Or how about "Delete any emails from Bob Thompson" or "Update all my apps, but delete 'Angry Birds Space.' I'm over it."