Document about x:Shared Attribute on MSDN:

The default value for x:Shared is true. It means that any given resource request always returns the same instance.

In the preview blog, the x:Shared property of Image control resource is true. So the Content of ContentControl is pointed to the same Image control.

<Border Background="Blue" Margin="10">
    <ContentControl Content="{StaticResource image}"/>

But the Image control has only one Parent in Logic Tree. So it just shows in the last ContentControl.

    <TextBlock Text="Third"/>
    <ContentControl Height="150"
         ContentTemplate="{DynamicResource dataTemplate}"/>

But if set the x:Shared=”false” for Image control, every time requesting the image resource, it will create a new Instance Image control. So, it will show 3 images.

From the MSDN, it explains there are two scenarios using x:Shared=”false”

One scenario for x:Shared="false" is if you define a FrameworkElement or FrameworkContentElement derived class as a resource and introduce the element resource into a content model. x:Shared="false" enables an element resource to be introduced multiple times in the same collection (such as a UIElementCollection). Without x:Shared="false" this would be illegal, because the collection enforces uniqueness of its contents. But the x:Shared="false" behavior basically creates another identical instance of the resource, rather than returning the same instance.

Another scenario for x:Shared="false" is if you use a Freezable resource for animation values, but want to modify the resource on a per animation basis.

In my application, it’s the first scenario.