What is BigPipe and What Does it Mean for Future Drupal Performance?

In a recent blog post by Dries Buytaert, the founder and lead developer of Drupal, he discussed various aspects of the "decoupling movement", pros and cons of various approaches, and how it relates to Drupal and its future design architecture. In his own words, "the term decoupled refers to a separation between the back end and one or more front ends instead of the traditional notion of service-oriented architecture."