EnableServicesFrameworkTracing is an Appsetting introduced in 7.0.
Setting this to true will enable WebAPI tracing withing the Services Framework this includes all the built-in WebAPI tracing as well as any custom tracing included in the services running on the site.
Enabling tracing has a small but noticeable performance impact. This setting defaults to false, and should be left disabled except in development situations and when debugging specific Service Framework issues.