and further into the long tail, sales may become so small that the marginal cost of tracking them in rank order, even at a digital scale, might be optimised well before a million titles, and certainly before infinite titles. This model can provide further predictions into markets with long-tail distribution, such as the basis for a model for optimizing the number of each individual item ordered, given its current sales rank and the total number of different titles stocked. Business models Competitive impact Before a long tail works, only the most popular products are generally offered. When the cost of inventory storage and distribution fall, a wide range of products become available. This can, in turn, have the effect of reducing demand for the most popular products. For example, a small website that focuses on niches of content can be threatened by a larger website which has a variety of information (such as Yahoo) Web content. The big website covers more variety while the small website has only a few niches to choose from. The competitive threat from these niche sites is reduced by the cost of establishing and maintaining them and the effort required for readers to track multiple small web sites. These factors have been transformed by easy and cheap web site software and the spread of RSS. Similarly, mass-market distributors like Blockbuster may be threatened by distributors like LoveFilm, which supply the titles that Blockbuster doesn't offer because they are not already very popular. Internet companies Some of the most successful Internet businesses have used the long tail as part of their business strategy. Examples include eBay (auctions), Yahoo! and Google (web search), Amazon (retail), and iTunes Store (music and podcasts), amongst the major companies, along with smaller Internet companies like Audible (audio books) and LoveFilm (video rental). These purely digital retailers also have almost no marginal cost, which is benefiting the online services, unlike physical retailers that have fixed limits on their products. The internet can still sell physical goods, but at an unlimited selection and with reviews and recommendations. The internet has opened up larger territories to sell and provide its products without being confined to just the "local Markets" such as physical retailers like Target or even Walmart. With the digital and hybrid retailers there is no longer a perimeter on market demands. Video and multiplayer online games The adoption of video games and