First, a personal voice is much better than no voice and no video, you gain trust by adding a video to your opt in page and you increase your sign up rate by adding a personal touch to a tried and tested opt in marketing method.

Also....

• You can explain the key benefits in person on video of why any subscribers should in fact sign up to your email list.
• You can cheekily integrate a product you have created or are an affiliate for and drop it in there somewhere, with a url or redirect to the url when they sign up.
• By adding your voice or face you are branding your offers whatever they may be, building a brand is what you shold be doing anyway, either you or your business logo and tag line.
• People are more responsive to video than simple words, if they feel entertained too all the better.
• The sky is the limit with video marketing, you could include a short tutorial style video, a sort of taster on what content is to follow in your email messages.
• You only have yourself to blame if your face and the words you speak cannot instill confidence for subscribers to take action.