I have one suggestion. Why not have a validate / verified account for some TripAdvisor free member to upgrade? e.g.:-
1. Members are required to pay a small amount e.g. of USD10 for validation process fees.
2. Members are required to send a copy of National Identity Card or National Passport for validation.
3. Members are required to send a copy of Utility Bills with their names on the bill for validation purpose. Once the applicant meets all the requirements above, then TripAdvisor will give them a special Logo or Badges somewhere on their profile picture. This is to tell other members or users that, the particular member has been validated or verified by TripAdvisor and Trusted.
Of Course, it will be easier for validated/verified members to get help from TripAdvisor helper when they are asking for any assistance in restorating or retrieving their accounts if accounts are lost.
Hope that my suggestion will help or improve TripAdvisor in managing the accounts.