Are you kidding?
It means that if you go to a coffes hop and plug your laptop, you can become compromised. Sure, random people in a starbucks won't, but it's a boon for industrial espionage!
I've never seen a coffee shop that supplied power adapters, it's always just a bunch of power outlets. I think your safe for now.
You're worrying for a coffee shop that doesn't even exist.
The provided iphone wall charger is 5 watts, the provided apple laptop charger is 60 watts.