PG was/is completely wrong. Twitter was supposed to be the new SMS, or text message protocol, but that never happened. RSS is an example of a protocol in that space. At best, Twitter was/is an API.

In a practical utility perspective Twitter was a pub/sub broadcast system in the social media space. It was slim, fast, and real time in a way the Facebook wasn’t, due to a 140 character limit. Yet, it never seemed to become more than 10% of Facebook and almost exclusively used only by people who were already heavy Facebook users.

I remember the optimism around Twitter in 2007 because it was immediately evident that it was addictive to certain personalities. Some people just had to broadcast absolutely everything they did, often irrationally. Most everyone else tried to find a use for Twitter but couldn’t. I know many early users that either abandoned or deleted their accounts before 2010.

Eventually it just became a text broadcast interface via their client. That is good for people who want to build a following, but nobody else found a use for it. In that regard YouTube is the Twitter replacement but YouTube had value otherwise that Twitter never could.