But the pace of technology is upending these rules and assumptions. Relationships that begin online, Jacob finds, move quickly. He chalks this up to a few things. First, familiarity is established during the messaging process, which also often involves a phone call. By the time two people meet face-to-face, they already have a level of intimacy. Second, if the woman is on a dating site, there’s a good chance she’s eager to connect. But for Jacob, the most crucial difference between online dating and meeting people in the “real” world is the sense of urgency. Occasionally, he has an acquaintance in common with a woman he meets online, but by and large she comes from a different social pool. “It’s not like we’re just going to run into each other again,” he says. “So you can’t afford to be too casual. It’s either ‘Let’s explore this’ or ‘See you later.’ ”