A user on the the doom9.org message boards has posted links to a program called FairUse4WM that is capable of removing Microsoft"s DRM 10, which protects files offered by "Plays For Sure" compatible music stores.
The program is an easy-to-use front end to an application called drmbg that strips DRM headers from "secure" WMA files. Although he apparently developed the program to allow people to play their legally purchased music on the device of their choice, the potential for abuse is fairly high.