Libraries that use DRM are submitting patrons to the onerous and unethical legal terms involved with purchasing, installing, and using software such as Microsoft Windows and the Windows Media Player. In the case of Microsoft Windows, this entails agreeing to terms that allow Microsoft to delete software and data that the user legally owns and has created or installed on their own machines. For a library to require their patrons to agree to such End User License Agreements as a prerequisite for gaining access to its collection is an injustice.Link (Thanks, Joshua!)
These software requirements drive the sales of DRM technology vendors, such as Microsoft and OverDrive, providing an incentive for patrons to discontinue using software and materials that do not impose DRM. The common argument that DRM and proprietary software are necessary because publishers require them becomes a self-fulfilling prophecy, because the library is using its own market power to encourage their use, hurting the emergence of competing alternatives in the process.