First version of Twitter's API had no authentication, it was as free and open as it can get, so it got integrated everywhere. Everyone without technical knowled

First version of Twitter's API had no authentication, it was as free and open as it can get, so it got integrated everywhere. Everyone without technical knowledge could copy and paste a snippet into their WP powered blog or website, deploy it and enjoy the functionality. I think that was one of the primary driving forces behind Twitter's growth. Putting an API behind a paywall basically eliminates the majority of Average Joe's