Why has it been difficult for media companies to sue internet file swapping organizations?

Due to the Anticybersquatting Consumer Protection Act (ACPA) that was enacted in 1999, it has become difficult for media companies to sue file swapping organizations. While some have been successful, the ACPA throws up many roadblocks. Some companies that offer domain name registrars have privacy services that allow the true owners of the web sites to remain hidden which makes it increasingly difficult to identify cybersquatters. Prior to filing a lawsuit, a trademark owner must request a subpoena to find the real and true identity of the website owner. Due to the immense cost of these filings and court costs, most of these disagreements and issued end up settling out of court.