Provided are a system and method to authenticate user identities. The method includes gathering metadata from at least one discussion involving at least one pre-defined user identity on a first social network. The method evaluates the metadata of at least one third party response related to a posting by the at least one pre-defined user identity. The at least one pre-defined user identity is authenticated based on the evaluated third party response. And an indication of authentication for the at least one pre-defined user identity is provided. The system and method may also permit bridging of the established authentication between different social networks.