That'd be nearly impossible. To build a case against each user, they would have to:
1) Identify potentially infringing files of sufficient value to constitute criminal copyright infringement
2) Identify accounts that uploaded those files
3) Verify that the account holder is a US citizen (jurisdiction)
4) Track down where that user distributed the links in order to collect evidence proving:
a) The infringement was willful
b) The infringement was of commercial advantage or private financial gain
5) Obtain a court order for each account to subpoena the identity of the account associated with the ISP of the uploader's IP address
6) Track down the current copyright holder of each potentially infringing work, and verify that the person identified was not licensed to reproduce or distribute the work (i.e. don't sue the label marketing agent for uploading a demo copy of their artist's song)
Now, you can prepare and file one case.