Everyone says that running processes as root is bad, since it defeats the security and privileges model. But what user should be used to run a startup process? Is it really necessary to create a new user, just to own a single startup process?
That depends. Things that run constantly (services, servers), have to write data etc., and, most importantly, interact and use untrustworthy data owned by someone else than root should get their own users.
Other startup processes do not require such security measures.