In the pre-Internet days, such protests may not had served much purpose, but today advertising a URL (such as www.jehovahs-witness.com) or a phone number (such as 1-800-Help4JW) might do great good for the apostate cause. Jehovah’s Witnesses would be too shy to approach an apostate at a convention, but can easily memorize or write down an easy to remember phone number or URL.
If the advertisement is off the convention site itself it cannot be stopped, except by extreme measures.