We – Manton Reece and Brent Simmons – have noticed that JSON has become the developers’ choice for APIs, and that developers will often go out of their way to avoid XML. JSON is simpler to read and write, and its less prone to bugs.
So we developed JSON Feed, a format similar to RSS and Atom but in JSON. It reflects the lessons learned from our years of work reading and publishing feeds.
Source: JSON Feed: Announcing JSON Feed
Edit: This is also supported in the feedparser gem for Ruby.