Up until now, there’s been an element of utopianism to Twitter—a communal sensibility, a sense of egalitariansim, a conviction of the value of conversation. A “social warmth,” Steven Johnson calls it in Time magazine’s current, Twitterphilic cover story.

Up until now, Twitter has been a space largely free of commercial concerns, a place where people could talk and share and explore without mercenary influences seeping into the interaction.

Up until now.

Megan Garber is an assistant editor at the Nieman Journalism Lab at Harvard University. She was formerly a CJR staff writer.