You can and should restrict the number of people with access to the data, but in a tech company there's always going to be a significant number of people with direct access to the raw data. Software engineers on an on-call rotation, full-time site reliability engineers, data analysts, maybe even some external contractors... maybe this isn't the case for Twitter, but many companies also have to put complete trust in their cloud provider or datacenter, which puts even more people in the loop.
Even if you follow best practices with access control, in the end you're always going to have a group of people who you need to trust with access to folks' personal data. Maybe the solution is better audit logging and even tighter access, but I'm not sure leaks of this nature are preventable.
Even if you follow best practices with access control, in the end you're always going to have a group of people who you need to trust with access to folks' personal data. Maybe the solution is better audit logging and even tighter access, but I'm not sure leaks of this nature are preventable.