Some notes on the Windows Server 2008 R2 Active Directory Recycle Bin Feature

• The Enable-ADOptionalFeature cmdlet must be run on the Schema Master DC (if not you will get A referral was returned from the server)
• The only valid value for the Scope parameter is ForestOrConfigurationSet, Domain is not vaild (If you try you will get The specified method is not supported)
• The Forest Functional Level must be Windows Server 2008 R2 mode
• You must be an Enterprise Admin
• The process is irreversible; you cannot turn off the Recycle Bin Feature once it is enabled

More info here:

• Active Directory Recycle Bin Step-by-Step Guide