Protecting your tweets is stupid. I understand you are trying to avoid bots; what you are actually doing is annoying real people. If you want to have private conversations with friends, create a separate twitter account. Your author twitter account should be open for everyone to see, whether or not they follow you.
Forcing someone sign up or provide an email address for your campaign MAY work if you make it worth their while. A smart way to do this is sending free ebooks through email. However, that is not viral marketing.
A virus should be contagious. You need people to spread it like the common cold. They need to be able to give (or share) the video with everyone they meet. So put the video where everyone can find it. To be viral, it needs to be on YouTube and you must allow embedding.
Also, like a virus, viral marketing is most effective BEFORE people realize it is viral marketing campaign. you want the video shared quickly. The buzz you generate should be about how interesting or entertaining the campaign is. If people are saying "Good marketing", the symptoms are visible and it is less contagious.
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