Twitter is building a 'subscription platform,' and paying for tweets might be a thing

"This site is free" is a common refrain on Twitter. Meant to be read in the tone of sarcastic disbelief, it's often brought out to highlight the absurdity of a situation that someone has, typically, stumbled ass-first into online — on full display for all Twitter users to witness in real time, free of charge. 

However, if a...