While music downloaders can be construed to be a technological measure to gain unauthorized access to a copyrighted work, and the DMCA prohibits such circumvention of technologies designed to protect copyrighted works, so far there haven’t been any bans on it.
Moreover, the Online Copyright Infringement Liability Limitation Act can be a way out for music downloaders through the Safe Harbor clause, which protects music downloader services from acts of direct copyright infringement, shifting the liability back to the user.
In other terms, music downloader operators can claim that they are only providing a service using cached links, thus, not being the ones making the materials available, nor the recipients of such materials. Therefore, operators can be interpreted to be only temporary and intermediate storage providers of such materials.
That being said, for the time being, neither users nor music downloader operators are being sued.