They always knew it. But they don't really need it because they can simply get the traffic from Internet providers. Hackers, on the other hand, can use it with great effect.
With great effort, you mean.
It's not an easy hack, as it relies on physical proximity, plus a bunch of fairly expensive hardware; And it is completely stymied by the use of SSL or a VPN - so it's usefulness to black-hats is quite restricted.
Just using the 'HTTPS Everywhere' browser plugin in Chrome or Firefox will prevent anyone from being able to do more than intercept and decrypt packets whose plaintext content is encrypted data.
This is a big problem, but not really a cause for panic. People just need to assume that their local network traffic is not secure, despite being inside a firewall - which frankly is an assumption we should all have been making to begin with.
After all, there are plenty of opportunities to grab (and/or spoof) HTTP traffic once it passes out to the Internet that don't require an attacker to even be on the same continent as their victim. If you are going to the trouble to park a black van outside your victim's home or office, then what's stopping you from tapping into the ADSL line coming from the building?
