At my previous job we used them. Sometimes it was to enable/disable features for customers that were part of a beta program. These could eventually evolve to be

At my previous job we used them. Sometimes it was to enable/disable features for customers that were part of a beta program. These could eventually evolve to be controlled by ad admin as we rolled out the feature to all customers. The product was a desktop file synchronization client. We had an API that we would get administer-controlled settings. Feature flags were usually part of that API. We don't use them at my current job, but it's a much smaller company with many less customers.