Where's the Visualforce viewstate coming from? How is it growing from Exhibit 5 to Exhibit 6?

PublicViewstateExhibit1.page

<apex:page sidebar="false" showHeader="false" standardStylesheets="false">
    <h1>
        Exhibit 1: No controller, no form
    </h1>
    <p>
        This Visualforce page uses no controller, standard or custom,
        and it also has no form on the page.
    </p>
</apex:page>

PublicViewstateExhibit2.page

<apex:page sidebar="false" showHeader="false" standardStylesheets="false"
           standardController="Lead">
    <h1>
        Exhibit 2: Standard Lead controller, no form
    </h1>
    <p>
        This page uses <code>standardController="Lead"</code>,
        but there is no <code>apex:form</code> on the page.
    </p>
</apex:page>

PublicViewstateExhibit3.page

<apex:page sidebar="false" showHeader="false" standardStylesheets="false"
           controller="PublicViewstateExhibit3Controller">
    <h1>
        Exhibit 3: Custom controller with persistent property, no form
    </h1>
    <p>
        This controller has a property defined as follows:
        <code>public Lead record { get; set; }</code>
    </p>
</apex:page>

PublicViewstateExhibit3Controller.cls

public class PublicViewstateExhibit3Controller {
    public Lead record { get; set; }
}

PublicViewstateExhibit4.page

<apex:page sidebar="false" showHeader="false" standardStylesheets="false">
    <h1>
        Exhibit 4: No controller, one form
    </h1>
    <apex:form>
        <p>
            This paragraph is enclosed in an <code>apex:form</code>
            on a page that uses no controller, standard or custom.
        </p>
    </apex:form>
</apex:page>

PublicViewstateExhibit5.page

<apex:page sidebar="false" showHeader="false" standardStylesheets="false">
    <h1>
        Exhibit 5: No controller, two forms
    </h1>
    <apex:form>
        <p>
            This paragraph is enclosed in an <code>apex:form</code>
            on a page that uses no controller, standard or custom.
        </p>
    </apex:form>
    <p>
        This second paragraph is <em>not</em> enclosed in an <code>apex:form</code>.
    </p>
    <apex:form>
        <p>
            This third paragraph is enclosed in a different <code>apex:form</code>
            on the same page.
        </p>
    </apex:form>
</apex:page>

PublicViewstateExhibit6.page

<apex:page sidebar="false" showHeader="false" standardStylesheets="false">
    <h1>
        Exhibit 6: No controller, two forms
    </h1>
    <apex:form>
        <p>
            This paragraph is enclosed in an <code>apex:form</code>
            on a page that uses no controller, standard or custom.
        </p>
    </apex:form>
    <p>
        This second paragraph is <em>not</em> enclosed in an <code>apex:form</code>.
    </p>
    <apex:form>
        <p>
            This third paragraph is enclosed in a different <code>apex:form</code>
            on the same page.
        </p>
    </apex:form>
    <p>
        If you compare this to
        <apex:outputLink value="{!URLFOR($Page.PublicViewstateExhibit5)}">Exhibit 5</apex:outputLink>,
        even though everything else on this page is identical except
        for this extra <code>p</code> element, the viewstate actually 
        has increased in size!
    </p>
</apex:page>