Microsoft urgently needs to consolidate all the APIs that are required for provisioning services or sites. The amount of knowledge you need to have and the number APIs you need to use in order to lock down a Web service or Enterprise Services application programmatically at installation time in order to have it run under an isolated user account (with a choice of local or domain account) that has the precise rights to do what it needs to do (but nothing else) is absolutely insane.
You need to set ACLs on the file system and the registry, you need to modify the local machine's security policy, you need to create accounts and add them to local groups, you must adhere to password policies with your auto-generated passwords, you need to conbfigure identities on Enterprise Services applications and IIS application pools, you need to set ACLs on Message Queues (if you use them), and you need to write WS-Policy documents to secure your WS front. Every single of these tasks uses a different API (and writing policies has none) and most of these jobs require explicit Win32 or COM interop. I have a complete wrapper for that functionality for my app now (which took way too long to write), but that really needs to be fixed on a platform level.