As far as I know the System.ComponentModel.DataAnnotations.DataTypeAttribute not works in model validation in MVC v1. For example,
public class Model
{
[Da
Like LukLed pointed out, DataTypeAttribute doesn't do any validation by default. But it does influence templates regarding how the data is presented.
For example if you call Html.DisplayFor() method on a model that has DataType(DataType.EmailAddress) attribute, it'll format its value with {0} (at least in MVC RC2).