PlaysForSure was a Microsoft logo program, launched in 2004, that identified devices (portable and networked) that were compatible with online music and video stores.
Essentially, the logo identified a store as using the latest version of Microsoft's Windows Media DRM scheme and ensured that a device could play content with that same DRM scheme. While the program was an improvement over the previous situation of no system at all, it wasn't as simple as Microsoft implied. For instance, there was one logo for subscription content, another for per-download content, and cross-compatibility wasn't guaranteed.
When Microsoft announced Zune in mid-2006, a lot of onlookers (including me) suggested it spelled doom for the company's PlaysForSure partners--the Zune team made no guarantee that the devices would be able to play PlaysForSure content, and material from the Zune Marketplace definitely does not play on PlaysForSure devices. Most of the company's former partners found alternatives--Samsung building its own music store, MTV teaming up with longtime Microsoft rival RealNetworks--even as Microsoft publicly insisted that the initiative was not dead, just pining for the fjords.
Today, one of my colleagues pointed out that Microsoft's no longer maintaining the facade: PlaysForSure has officially been rolled into another logo program, Certified for Windows Vista. The old compatibility guidelines and tests for device partners are still in place, but the brand will quietly disappear into the annals of market failures.