You are in control of what people can see, and you can easily and immediately deactivate your showcase.
Deactivate your showcase via the following method:
Step 1: Click on 'My showcase' in your portfolio
and select 'Edit my Showcase'
Step 2: Click on 'Next step'
You will now see the references that are displayed in your showcase and can proceed immediately to 'Next step'.
Step 3: Deactivate your showcase by clicking on 'Deactivate link'
Your showcase has now been deactivated.