mitmproxy dev here, very awesome! :) This seems to be particularly useful to quickly generate clients for reverse-engineered APIs.
AirBnB doesn't have an official API but changes the tags so often that scrapers people put up on Github go out of date quickly. Now I can run this whenever I want to have actual search functionality (instead of the hobbled crap available on the website) and ensure that whatever flavor of API is available on the website that day is easily queryable!