SQL 2012 can use Managed Service Accounts and Virtual Local Accounts as described here: http://msdn.microsoft.com/en-us/library/ms143504%28SQL.110%29.aspx#New_Accounts
Installing CRM 2013 works with the default virtual local accounts created when installing SQL 2012.
However, installing Reporting Extensions reports an error that a local account is used for Reporting Services and this must be changed to a domain account.