Products with higher user engagement have the potential to grow faster than their rivals.

Like flossing, frequent engagement with a product, especially over a short period of time, increases the likelihood of forming new routines.

When designers intentionally trick users into inviting friends or blasting a message to their social networks, they may see some initial growth, but it comes at the expense of users' goodwill and trust. When people discover they've been duped, they vent their frustration and stop using the product.

Habit-forming products alleviate users' pain by relieving a pronounced itch.

You'll often find that people's declared preferences - what they say they want - are far different from their revealed preferences - what they actually do.

Instead of relying on expensive marketing, habit-forming companies link their services to the users' daily routines and emotions.

Reducing the thinking required to take the next action increases the likelihood of the desired behavior occurring unconsciously.