First let's read what it says:
Your hostname should be a Fully Qualified Domain Name that will not be used elsewhere on the server. You should never set your hostname to an name that is already used (www, ftp, mail, etc) or to the name of an account on the server (www.domain.com)
Now honestly I know it is OK to have the actual domain name of your company (which also exists in the list of accounts most likely) AS PART of the hostname. Many do this and that is OK. What is not OK is to have the same fully qualified domain name (ie: www.blurstorm.com
) as the hostname itself. But if it is part of the hostname (ie: whm.blurstorm.com) and resolves properly then that is acceptable.