Robinson Meyer wrote a great essay in The Atlantic about the difference between saying and writing on Twitter:
On Twitter, people say things that they think of as ephemeral and chatty. Their utterances are then treated as unequivocal political statements by people outside the conversation. Because there’s a kind of sensationalistic value in interpreting someone’s chattiness in partisan terms, tweets “are taken up as magnum opi to be leapt upon and eviscerated, not only by ideological opponents or threatened employers but by in-network peers.”
Anthropologists who study digital spaces have diagnosed that a common problem of online communication is “context collapse.” This plays with the oral-literate distinction: When you speak face-to-face, you’re always judging what you’re saying by the reaction of the person you’re speaking to. But when you write (or make a video or a podcast) online, what you’re saying can go anywhere, get read by anyone, and suddenly your words are finding audiences you never imagined you were speaking to.