[jQuery] $(form).serialize() does not include submit button data

I was wondering if this is a bug or not ...  here's the full example:
http://andric.us/media/tmp/jquery-form.html

I would think the submit button data would also be included when doing
$(form_obj).serialize()?  Apologies if this has already been answered
somewhere already.  It can easily be remedied by including some extra
hidden fields but I thought I would ask about it.

The code looks something like:

<script type="text/javascript">
    function postSubmit(data) {
        $('#messages').text(data);
    }
    $(document).ready(function(){
        $('input[type="submit"]').click(function(event){
            var data = $(this.form).serialize()
            $('#messages').text(data);
            //$.post("", data, postSubmit);
            return false;
        });
    });

[snip]
<ul>
<li>

    <p>Here's a form with just a submit button:</p>
        <form action="" method="post">
            <ul><li>
            <input type="submit" name="update_project" value="Update" /
>
            </li></ul>

        </form>
</li>

<li>

    <p>Here's a form with some hidden fields:</p>
    <form action="" method="post">
    <ul><li>
    <input type="hidden" name="build" value="0044" />
    <input type="hidden" name="push_build" value="Deploy" />
    <input type="submit" name="push_build" value="Deploy" />
    </li></ul>
    </form>

</li>
</ul>

[snip]

TIA,

--
Milan