I'm a Chinese software developer. In China, VPN or other proxy tools are essential for anyone who need look up serious technical materials online. We call it "翻墙"(Go Over the Wall), which is a basic skill.

And about the reason why these sites are blocked: just BECAUSE THEY CAN! (They even blocked github for mysterious purpose once!) There is no public rule/law/principle to tell us why a foreign site is blocked. The just kill sites silently and pretend nobody cares.

Fortunately enough, HackNews has not been blocked, yet.

(Sorry for my bad English)