Valve announced yesterday that their extension of Steam, called Steam Cloud, will launch later this week with the Left 4 Dead demo. Steam Cloud is "a set of services for Steam that stores application data online and allows user experiences to be consistent from any PC." We discussed an early announcement for it back in May. Valve adds that "Steam Cloud will be available to all publishers and developers using Steam, free of charge, and Valve will add Cloud support to its back catalog of Steam games. Cloud services are compatible with games purchased via Steam, at retail, and other digital outlets."