What happens if you have attrition in your customer base over time. An easy way to extend the model to take this into consideration would be to add a variable to model Attrition Rate as a percentage of the entire installed base at each cycle, and simply subract this from the total population at each cycle. This topic is nicely covered in this blog post by Andrew Chen: Is your website a leaky bucket? 4 scenarios for user retention.
For example, you might take photos and have them available for a fee at sites such as shutterstock.com or istockphoto.com. Similarly, you can create and upload designs at sites such as zazzle.com and cafepress.com, where people can buy them imprinted on shirts, mugs, and so on. Similarly, if you write an e-book (which can be as short as 6,000 or so words), you might find that people are interested in buying it, perhaps via Amazon.com's direct publishing service.
As mentioned earlier, most platforms have an algorithm in place to determine the type of content that gets marked as viral, trending, popular, or hot content. In most cases, these algorithms look for engagement a piece of content receives in relation to the time that piece of content was published or in a specific timeframe. Let’s say that your viral marketing goal was to create a video that made the Trending charts on YouTube. Your video would have a shot if:
The reason to make use or virality, the ease in spreading and sharing, is however a double-edged sword. We cannot forget that in this type of campaign, a large part of the control falls into the hands of the users, and we risk the message being misinterpreted or parodied. On the other hand, a successful viral campaign can work miracles for your brand’s results.