“You can't really plan for virality but you can at least sow the seeds and see if they germinate. If you don't cultivate the right conditions for virality to occur it never will. If you have the ability to share content, put those share features in — then at least you can see the natural predilection of users to share.”

Plant the seeds of virality even if you can't plan for it

Andy's pragmatic take on viral loops: build the cheap share/referral surfaces during the growth phase so you can observe whether organic sharing happens. Even small amounts lower blended CAC; occasionally you'll catch fire. Don't engineer virality, but don't preclude it either.