Data Annotation Attributes Not Working Using Buddy Class Metadata In An MVC App?

I have found hints that MVC 2 recognises the 'buddy class' type of property metadata, where data annotation attributes are applied to a 'buddy' metadata class, and the MetadataType on the actual entity class points to that buddy class, as below. However, as below, it seems the only attribute that makes any difference to the rendered UI is DisplayName. Why are the other attributes like DataType, Required, and ReadOnly not working? I.e. why can I enter text in a read only field? Why do I not get an error when a required field is empty? Why does the DataType attribute have no apparent effect? Why does EditorForModel not include validation messages?

[MetadataType(typeof(CustomerMetadata))]
public partial class Customer
{
public class CustomerMetadata
{
[ScaffoldColumn(false)]
public object CustomerId { get; set; }
[DisplayName("CustomerNo.")]
[ReadOnly(true)]
[Required(AllowEmptyStrings = false, ErrorMessage = "Customer No. is required.")]
public object CustomerNo { get; set; }
}
}

I find behaviour the same whether I use an explicit LabelFor and TextBoxFor for each model property, or a single EditorForModel for the whole model.