Markets and business models
Consumer virality
Paid acquisition is an auction against every other app. Organic loops and retention are usually the only affordable growth at consumer ARPU.
Paid user acquisition for consumer products is an auction against Meta, Google, TikTok and every other app. Bids rise to the LTV of the best competitors. If your LTV is thin, paid alone will not work.
Organic channels that can escape the auction: word of mouth and invites (the product is better with others), content / SEO / UGC (artifacts leave the product and pull people in), and platform distribution (App Store featuring, embeds, browser defaults). Platform distribution is fragile — see platform risk.
Concept
A growth loop is a closed cycle where output of one step feeds the next (user creates content → content ranks → new user signs up → creates content). Loops beat one-off campaigns because they compound. See growth loops for product mechanics. Here the economic point is that loops reduce paid dependency.
The classic viral factor (k-factor): if each user brings invites × conversion new users, and that product is greater than 1, growth compounds without ads. In practice k > 1 is rare and unstable. More often you get a helpful organic fraction that lowers blended CAC.
Walking through blended CAC
Model blended CAC = total acquisition spend / new users, and separately paid CAC and organic share. A product that is 70% organic can afford worse paid efficiency than one that is 90% paid. Boards that only see blended CAC miss when organic is dying.
From the subscription sketch: price $10/month, store fee ~30%, net ≈ $7, lifetime 8 months, LTV ≈ $56.
Blended CAC $35 → LTV/CAC ≈ 1.6× (fragile)
Blended CAC $15 → LTV/CAC ≈ 3.7× (healthier)The $15 path is usually "more organic," not "cheaper ads." Retention multiplies virality: a retained user gets many shots to invite or share; a one-session tourist gets one. Andrew Chen's point: improving retention is often the highest-leverage viral strategy — not adding more invite spam.
Common mistakes
- Reading only blended CAC. Organic can be dying while the blend still looks fine.
- Invite spam instead of retention. Tourists do not invite. Habit does.
- Planning on k > 1. Treat it as a bonus, not a plan.
Check yourself
LTV $56, blended CAC $35 vs $15. What changed the ratio?
Organic share (or much better paid efficiency). 56/35 ≈ 1.6×; 56/15 ≈ 3.7×.
Why is retention a viral strategy?
A retained user gets many chances to invite or share. A one-session tourist gets one.
Key takeaways
- Paid consumer acquisition is an auction. Thin LTV loses.
- Organic loops lower blended CAC. Measure paid and organic separately.
- k > 1 is rare. Plan for a helpful organic fraction, not a perpetual motion machine.
- Retention powers virality. Fix the curve before adding invite features.
Further learning
Why the best way to drive viral growth is to increase retention (Andrew Chen)Why the best way to drive viral growth to increase retention and engagement at andrewchenandrewchen.comNext, how to measure consumer retention.