viral marketing comes in many forms. Whether it's packaging up a game with a product to entice people to buy it, or using a game itself to bring people to your website. People pass games around an office and generally starts with just one person, they in turn send it around to people in their email address books in other offices and then you start seeing a chain reaction develop. So you don't always have to spend money on advertising to do it, but it helps to create several chains. Generall called seeding, the seed sprouts and grows, then forms other seed chains. Some viral chains do better than others, some fade away and other grow stronger and longer. It doesn't have to be games, it can be videos, blogs, websites with gimmicks on, but generally something that people want to pass around.