Users who continually find value in a product are more likely to tell their friends about it.

Why not live now instead of someday?

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

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

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.

Many innovations fail because consumers irrationally overvalue the old while companies irrationally overvalue the new.

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