[haddr]

I will work with any data, as soon as it is easily retrieved with some css selector. Otherwise you would have problems using any web scraping tool.

[sixtypoundhound]

JSON is pretty easy to unpack, if you can figure out the call back that gets the data.

[minimaxir]

The primary use case for web scraping tools like Rvest is for data that doesn't have a JSON endpoint and everything is rendered serverside, or is a static web page.