With Event Sourcing, everything is traceble to the very beginning, so also user creation. In our system we do user creation and admin stuff over a public API. We have a (quite common) security rule: Only Admin users may delete users and give privileges to other users, i.e. to make them Admin.
In case of ES, how would you provision the system right after clean install? This can be the case when doing sandboxed integration tests.
Sorry for this rather philosophical question :)