Tightly coupled systems, on the other hand, where changes affecting one node swiftly affect others, are prone to cascading failures. Usenet was one such system, where an entire newsgroup could be ruined by a spreading flamewar. If a blogger flamed, people could just ignore the blog; when a Usenet user flamed, others got sucked in until the channel was filled with people yelling at each other. (As Nick Denton wrote, the blogosphere “routes around idiots” in a way that Usenet didn’t, because if didn’t depend on the common channel that a Usenet group did.)

Twitter is more like Usenet than blogs, but in many ways it’s worse. Like Usenet it’s tightly coupled. The “retweet,” “comment” and “like” buttons are immediate. A retweet sends a posting, no matter how angry or misinformed, to all the retweeter’s followers, who can then do the same to their followers, and so on, in a runaway chain reaction.

Unlike blogs, little to no thought is required (the character limit discourages it), and in practice very few people even follow the link (if there is one) to “read the whole thing.” The “block” and “mute” functions on Twitter are intended to protect against Usenet-style flamewars, but to the extent that they work, they also put people in bubbles of similar thinkers, which tends to encourage the spread of misinformation so long as it matches the thinkers’ prejudices.