One approach is to collaborate with relevant “legacy” governing bodies for a candidate group (industry lobbies, advisory boards, et cetera) and offering them the responsibility of curating an initial set of registrants. The motivation behind this approach is to leverage the industry expertise of the vetted curators in order to produce a compelling base set of registry listings.
Happily, the security properties of token-curated registries against such majority validator attacks are rather similar to those of Casper. In economic 51% attacks, the attacker’s weapon can be destroyed in a hard fork. As per Vitalik, “the intention is to make 51% attacks extremely expensive, so that even a majority of validators working together cannot roll back finalized blocks without undertaking an extremely large economic loss — a loss so large that a successful attack would likely on net increase the price of the underlying cryptocurrency as the market would more strongly react to the reduction in total coin supply than it would to the need for an emergency hard fork to correct the attack.” In token-curated registries, the validators are token holders.