Marketing flywheel
HubSpot's replacement for the funnel: instead of ending at purchase, happy customers feed growth through referrals, reviews and expansion, so the model is a wheel that spins faster as friction is removed. A useful corrective to funnel thinking wherever word of mouth and retention drive the economics.
Where it's used
Used in growth strategy for SaaS, marketplaces and subscriptions. Good for finding the customer-driven loops that lower acquisition costs over time.
Example
Customers who bring customers
DropboxDropbox gave you and the friend you invited free storage each: 250MB at first, later 500MB. More storage made you use it more, shared folders pulled in colleagues, and they invited others. Its founder reported a jump of about 60% in signups. The wheel kept turning with no new ad budget, and the customers were the ones spinning it.