There’s no way to prevent these things categorically but they can be made harder. A few ways (some more heavy handed than others and not always appropriate):
Requiring a verified email address.
Requiring a verified phone number.
Requiring a verified credit card.
Charging a nominal membership fee (e.g. $1/month) which makes scaling up operations expensive.
Requiring a verified ID (not tied to the account, but can prevent duplicates).
In small forums, reputation matters. But it’s not scalable. Limiting the size of groups to ~100 members might work, with memberships by invite only.
Requiring a verified email address.
Requiring a verified phone number.
Requiring a verified credit card.
Charging a nominal membership fee (e.g. $1/month) which makes scaling up operations expensive.
Requiring a verified ID (not tied to the account, but can prevent duplicates).
In small forums, reputation matters. But it’s not scalable. Limiting the size of groups to ~100 members might work, with memberships by invite only.