@mcc Twitter was also a “proprietary service operated by a single company, but with an unusually good ‘API’ for plug-in 3rdparty tools” until they dramatically locked it down in May 2012 and banned third-party clients.
I remember that moment well. It led to a wave of migration to a federated, open-source alternative: Tent.
For a moment I really thought Tent was gonna change the world. Fun time capsule now: https://scott.mn/2012/10/20/tent/