If you were smart enough to hack 23andMe to get genetic data to find a specific person, you'd be smart enough to reconstruct identities from publicly available data. You'd just have to cross-reference public anonymous databases with public non-anonymous ones. Both of which exist, and are free.
So far, the only real use-case for doing this is people trying to identify criminals from just DNA.
You realize this data is often available for purchase or eventually publicly leaked, right? You don't have to be "smart enough" to do the hacking to benefit from it.
So far, the only real use-case for doing this is people trying to identify criminals from just DNA.