And sometimes, entire nations. Qatar used to share a single IPv4 address, which I found out when news articles started reporting that the entire country could no longer edit Wikipedia without an account, which at the time, was also restricted if your IP was banned from anonymous edits. If you didn't create an account prior to the ban, you were completely blocked from editing.
https://en.wikipedia.org/wiki/User:82.148.97.69
https://techcrunch.com/2007/01/01/wikipedia-bans-qatar/