Portal centralization is an major shift for developers. It allows them to reach all potential customers through one shop, which takes care of the administrative tasks, such as billing and advertising. On top of these deployment facilities comes the fact that platforms providing centralized portals count on application sales to increase their revenue and therefore heavily promote application downloads and thus widely increasing the pool of potential consumers. This promotion is mostly done through advertising, but more importantly through greatly enhanced user interfaces. Before the emergence of centralized portals it took a expert user to download and install third-party applications, usually involving an internet search and a credit card payment, on a personal computer and then a file transfer via Bluetooth. Now it has become a "one-click" operation directly executable on the mobile device. Moreover, platforms can leverage on user communities which also promote applications using the reviewing features of the shops. A negative side of strong centralization for developers is that they might have to conform to certain rules defined by the portal provider. This problem can be observed with Apple's AppStore, which rules over which applications will be sold and which will be banned based on non-transparent criteria. To overcome these restrictions, the developer community has built alternative portals (Installer, Cydia) where developers can publish their applications. Unfortunately, only tech-savvy customers shop on such black markets, since phones must undergo a "jailbreak" procedure before they can access them.