Such devices are popular with manufacturers of many products as they offer an attractive business model (sell the trusted client at a loss, but make a profit by forcing the consumer to buy the associated service from the same manufacturer at an inflated price), and have a long history - an early example were radio receivers that were subsidised by broadcasters but restricted to receiving the subsidising broadcaster's reception. Modern examples include video recorders (which, by law, must include Macrovision anti-copying devices), DVD players (which, as well as Macrovision encoders to prevent copying onto video tape with standard consumer devices, must support CSS), video game consoles, which contain similar region-coding measures as well as devices to prevent any game unauthorised by the console manufacturer from working on that console, as well as the previously-mentioned network video games.
Despite the best efforts of manufacturers, technically-savvy consumers and other manufacturers have managed to bypass the limiting features of most trusted clients - from the simple replacement of the fixed tuning potentiometer in those early radios to the successful cryptographic attack on CSS in 1999. Manufacturers have therefore resorted to legal threats to prevent their circumvention, with varying degrees of success.
Microsoft's NGSCB aims to establish the trustworthyness which the MPAA needs to see a computer with NGSCB activiated as a trusted client.