Earlier quoted context omitted.
It seems like the AggregateIQ case shows the problem with this - by obeying the request, they admit that the EU has jurisdiction over them. That's probably the wrong thing to do when they have no connection to the EU, other than people from the EU choosing to connect to a server hosted elsewhere. It's probably the same reason why Hacker News does nothing to comply with the GDPR.
Jurisdiction is a tricky concept in cases like these where we are dealing with digital content. AggregateIQ could have ignored the GDPR-request, ignored any rulings and keep chugging along as long as they stuck to Canada (assuming Canada was not going to side with the EU). In short, if you're not in the EU, do not care about EU and never will, you can largely ignore the GDPR. Same as if some banana republic dictator…
That's not entirely true. You can go to a Canadian court to enforce an EU judgement against assets in Canada. So for example, if you cause a car accident in Germany, the plaintiff can sue you in Germany to get a judgement and then sue you in Canada to enforce that judgement. How Canadian (or US or otherwise) courts will treat a GDPR judgement remains to be seen, but it's not a guarantee that it won't be enforced.