Smartphone-only apps: consequences of limiting one account per phone number?

For smartphone-only apps that require each user to be a person (apps where there is no room for people to have multiple accounts), what are the negative consequences of limiting each phone number to one account creation? Assume that the logistics behind people changing their numbers and preserving their accounts is handled gracefully, does the concept of limiting one account per number pose a significant hindrance in any way? I don't know any people who share a mobile number or a phone, but that "data" is purely speculative and anecdotal--maybe lots of people do?

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