When I look in CiviCRM 4.6.8 at the custom field group settings associated with organization contact, then I see a select box where I can choose the type of organization type (as defined in Customize data and screens >> Contact types).
When I compare that with the custom field group setting associated with an individual, then I don't see this select box and I can therefore not restrict the field group to a custom individual contact type.
Is this to be considered by design or is this a bug being fixed in 4.6.9? To me it seems at least inconsistent. Please note that I have both custom individual and organization contact types defined.