The expanded previews are actually a new-ish Twitter card ("Summary card with large image"), and you'll only see auto-expanded links from publishers that have enabled the card on their sites. But expect most big publishers to follow suit, because the big, colorful cards get around Twitter's 140-character limit by inserting the first few words of the article in addition to the promotional tweet. And of course advertisers, who are just as thirsty for those favs and RTs, are likely to adopt them en masse as well.

It may be tempting to yell at Twitter for continually lowering the information density of its timeline in favor of big, dumb pictures. But publishers and advertisers had essentially hacked together a version of this card already, by tweeting an image along with every link because their metrics showed that it boosted the sacred metric of engagement. So blame the brands, for this and basically everything else.