Not at all! Viral Marketing describes any strategy that encourages individuals to pass on a marketing message to others, creating the potential for growth in message's exposure and influence. It also increases the chance of that individual to come back to the site:
For instance, a monthly newsletter signup is an excellent strategy to get customers to return to your site. After all, if they are signing up for a free monthly newsletter, they already have interest in your product, right?
If you setup a newsletter that is informative, timely, and provides free and useful information to your customers, chances are they are going to come back. They are also reminded on a monthly basis of your existence, something that is very important. The more a client is reminded of your existence, the more likely they are to refer you. This is the essence of viral marketing.
Or course, when you deliver that newsletter, you can also remind your previous customers about product reviews and notification of specials - and that is a great way to increase sales.