Applications we build are more and more dependent on 3rd party data sources. And as Internet of things continues to grow, this fact becomes even more stronger.
It allows us to create great experiences for the app end users by presenting them data gathered from across the Internets. But at the same time we have to spend more time ensuring that our applications are consuming all this data securely and they only get access to the data they need. OAuth protocol was designed and developed for this exact reason.