Wikipedia is also banned. Most social media is banned. Though these sites are generally allowed in HK. Many people also do use VPNs, but that's a different topic.
Let me clarify: Wikipedia is banned in Mainland China (what Westerners mean when they say "China"). It is allowed in Hong Kong and Taiwan - which are outside the great firewall. That doesn't mean they aren't censoring and editing the Chinese language Wikipedia. They definitely are. Also consider that many people from China (read: mainland China) are coming to the US and the west for school. They tend to read the Chinese language versions of Wiki, not the English ones.