Distributing x.509 is always a painful thing, and using WCF, it no long is.

In the WCF configuration, there is a knob in the configuration which helps the client to get the public key portion of the certificate in an "SSL" fashion.

     <bindings>
      <wsHttpBinding>
        <!--
        This configuration defines the security mode as Message and
        the clientCredentialType as Username.
        -->
        <binding name="Binding1">
          <security mode="Message">
                 <message clientCredentialType="UserName" negotiateServiceCredential="true"/>
          </security>
        </binding>
      </wsHttpBinding>
    </bindings>

It could apply to other bindings as well. This is username(client) over certificate(server) scenario.

This feature will make x509 certificate more popular with web service!