C# Send both HTML and Text email - most elegant?

Is it best practice to send both HTML and Text email?

If I only send HTML what are the dangers?

I'm thinking something like this below, from http://johnnycoder.com/blog/2009/04/15/net-mailmessage-linkedresources-alternateviews-and-exceptions/.

try
{
    // Assign a sender, recipient and subject to new mail message
    MailAddress sender =
        new MailAddress("sender@johnnycoder.com", "Sender");

    MailAddress recipient =
        new MailAddress("recipient@johnnycoder.com", "Recipient");

    MailMessage m = new MailMessage(sender, recipient);
    m.Subject = "Test Message";

    // Define the plain text alternate view and add to message
    string plainTextBody =
        "You must use an email client that supports HTML messages";

    AlternateView plainTextView =
        AlternateView.CreateAlternateViewFromString(
            plainTextBody, null, MediaTypeNames.Text.Plain);

    m.AlternateViews.Add(plainTextView);

    // Define the html alternate view with embedded image and
    // add to message. To reference images attached as linked
    // resources from your HTML message body, use "cid:contentID"
    // in the <img> tag...
    string htmlBody =
        "<html><body><h1>Picture</h1><br>" +
        "<img src=\"cid:SampleImage\"></body></html>";

    AlternateView htmlView =
        AlternateView.CreateAlternateViewFromString(
            htmlBody, null, MediaTypeNames.Text.Html);

    // ...and then define the actual LinkedResource matching the
    // ContentID property as found in the image tag. In this case,
    // the HTML message includes the tag
    // <img src=\"cid:SampleImage\"> and the following
    // Linke