If that oil tanker had a few RPGs and people that knew how to use them, there wouldn't be a problem. As other people have said these are fishing boats.
Sure, that would work really well...
"We're being boarded!"
"Hold them off a little longer, I only need 471 experience points before my magic-user will be able to cast Fireball!"
The best they could really do with the addresses would be to track down the ISPs of the users. The ISPs would then be faced with spending time (== money) to link an IP and time-window to an actual user, and then inform that user.
Their reward for this effort would be to have one of their technical support people spend an hour on the phone explaining to a clueless and scared someone that they needed to reinstall their XP & applications. This, they ultimately would not do.
A penny saved is a penny to squander. -- Ambrose Bierce
