Growth hacking produced a genre of case study built on a handful of examples, most of which are misremembered.
What the famous cases actually were
The referral programmes that are cited constantly worked because the product had genuine value that users wanted to share, and because the incentive was aligned with the product's core value.
Which means the mechanism was inseparable from the product, and copying the mechanism without the product produces nothing.
The email signature link cited as a foundational example worked in a specific moment when the product was novel and the channel was uncluttered.
Both are frequently presented as reproducible tactics, which they are not.
Channel decay
The pattern that determines the life of any acquisition tactic.
A channel that works attracts entrants, which raises costs and reduces response rates, until the returns approach the returns available elsewhere.
Which means any publicly discussed tactic is already in decline by the time it is written up.
The advantage goes to whoever finds a channel before it is crowded, which is a discovery problem rather than an execution one.
The retention foundation
The observation that survived from the whole movement.
Acquiring users who do not stay produces nothing, and spending on acquisition before retention is established wastes money at scale.
Which is why cohort retention curves are the first thing anyone competent asks about, and why a flattening retention curve is the signal that a product has found a durable audience.
A curve that continues declining toward zero means the product is not retaining anyone, and no acquisition spend fixes that.
Product-led growth
The more durable idea that came out of the same period.
Building acquisition and expansion into the product itself — free tiers, collaboration features that require inviting others, usage-based expansion.
Which works because it does not decay in the way channels do, and because the cost structure differs fundamentally from paid acquisition.
It requires a product where usage naturally involves others or grows with the customer, which is not every product.
Virality and what it actually requires
A viral coefficient above one means each user brings more than one further user, which produces exponential growth.
Which is extremely rare and generally short-lived, since it requires that the referral rate hold as the addressable population saturates.
Most products described as viral have coefficients well below one, where referral reduces effective acquisition cost without producing self-sustaining growth.
That is genuinely valuable and it is a different thing.
The cost discipline
The economics that eventually asserted themselves.
Customer acquisition cost against lifetime value determines whether paid growth is a business or a subsidy.
Payback period — how long until a customer has repaid their acquisition cost — determines how much capital growth consumes.
Which became the central question when funding conditions changed, and a large number of companies discovered their growth had been funded rather than earned.
What is actually reproducible
Measuring retention properly and by cohort.
Understanding the acquisition economics per channel including all costs.
Testing systematically rather than copying tactics.
And building whatever growth mechanism suits the specific product, which requires understanding the product rather than the case studies.
The onboarding moment
Where the most reliable gains actually sit.
Getting a new user to the point where the product delivers its value, as quickly as possible, has consistent effects on retention.
Which requires identifying what that moment actually is, empirically, by comparing users who retained with those who did not.
The commonly cited examples of specific action thresholds predicting retention were correlational, and treating them as targets to be driven produced mixed results.
The underlying principle — reduce time to value — holds regardless.
Referral programme design
Two-sided incentives, where both referrer and referred benefit, generally outperform one-sided ones.
The reward should relate to the product's core value rather than being cash, since cash attracts people who want cash.
And the moment of asking matters more than the offer, since a request made immediately after a positive experience converts far better than one made at random.
Measurement discipline
Growth teams that measured against a single business metric outperformed those optimising channel-level figures, because channel metrics can improve while the business does not.
Content and search
The channel that has changed most and remains substantial.
Content built for search worked well when supply was limited, and it has become considerably harder as volume grew and as search interfaces changed.
Which favours depth and genuine expertise over volume, since undifferentiated content no longer accumulates traffic the way it did.
Owned channels — email lists, communities — are less exposed to platform changes, which is why they have regained attention.
Partnerships
Distribution through another company's existing relationship with its customers.
Which is slow to arrange and durable once established, and it does not decay in the way advertising channels do.