On the Web, there are two main kinds of companies: marketplaces and attention economies.

Marketplaces operate by connecting one group of people to another group of people and allowing them to conduct a transaction, of which they take a cut. Etsy connects buyers to sellers; Kickstarter connects creators to backers; Airbnb connects travelers to hosts; OkCupid connects daters to daters. Marketplace companies build tools to solve problems that exist in the world. At their best, they operate like healers — mixing up medicine to answer a need.

Attention economies operate by convincing users to spend large amounts of time online, clicking many things, and viewing many ads. These companies often masquerade as “communication tools” that help people “connect”. But in attention economies, most of the “connecting” happens alone, while you’re staring at a screen, and it often leaves you feeling empty. Attention economy companies operate less like healers and more like dealers — creating addictive experiences to keep people hooked.

Both kinds of companies fulfill urges that are already in us, but the way that they answer those urges is different.

Marketplaces aim to eliminate urges by feeding them quickly (find a date, book a room, etc.), while attention economies aim to keep the urges going forever (continuous updates, another cool video, more new messages, etc.).

There is an ancient pact between tools and their users which says that tools should be used by their users, and not the other way around. Good tools should help their users accomplish a task by satisfying some pre-existing urge and then getting out of the way. Attention economies, at their most addictive, violate this pact.

Like good medicine, good tools should appear briefly when you need them, and then disappear, leaving you free to get on with your life.