On the iPhone, the always-on "Hey Siri" activation is actually local on the device. You can test this out by activating Airplane Mode and saying "Hey Siri". The interface comes up, then says that you can't use Siri because you're offline.
This means that Apple isn't listening to you 24/7, only when Siri is activated. Sure, sometimes it's activated accidentally and might overhear something you didn't want it to, but those times are pretty rare.
If Apple introduces a "Hey Siri" feature on the Mac (which it's unclear about given the fact that in the demo Craig activated Siri by clicking on the icon, then later by pressing a key on the keyboard), I expect it would operate in the same way.
Finally, I'm sure there's a software setting you can use to disable Siri if you really don't want it to be activated.
| This means that Apple isn't listening to you 24/7, only when Siri is activated.
what?! your proof that Apple isn't listening 24/7 is not a proof at all. A device that is listening to you 24/7 to hear when you say "hey Siri" can tell you "you can't use it because you are not online" whenever it wants to, and I don't think anybody was suggesting that Apple servers were capable of listening in when you have no network.
Apple has been shown in the past to log information on the device itself, however.
This means that Apple isn't listening to you 24/7, only when Siri is activated. Sure, sometimes it's activated accidentally and might overhear something you didn't want it to, but those times are pretty rare.
If Apple introduces a "Hey Siri" feature on the Mac (which it's unclear about given the fact that in the demo Craig activated Siri by clicking on the icon, then later by pressing a key on the keyboard), I expect it would operate in the same way.
Finally, I'm sure there's a software setting you can use to disable Siri if you really don't want it to be activated.