As long as you are using it within your Network or LAN (Local Area Network) you created, the streaming signal is staying within it. Nothing will leave outside of your network, everything is local. Unless you want to access your SlingBox outside of your network, them you are not in a LAN. It becomes a WAN (Wide Area Network). Then you are essentially using the internet to access your box.
but is this valid also if I am watching my tv, inside my LAN, but through the webapp on watch.slingbox.com?
It looks like the mac desktop app will be discontinued.. that's why I'm asking...
tnx a lot!