Two of the defendants argued their innocence on Sunday in a webcast
The founders of a website which carries links to copies of music, films and TV programmes have gone on trial in Sweden on charges of copyright theft.
The Pirate Bay is the world's most high-profile file-sharing site and is being taken to court by media firms including Sony and Warner Bros.
The men face up to two years in prison and a fine of $143,500, if convicted.
"File-sharing services can be used both legally and illegally," defence lawyer Per Samuelsson said.
Frederik Neij, Gottfrid Svartholm Warg, Peter Sunde Kolmsioppi and Carl Lundstrom have portrayed themselves as digital libertarians and say that they cannot be prosecuted for copyright theft because none of the content is hosted on their computer servers.
The men are accused of "promoting other people's infringements of copyright laws", according to charges filed by senior public prosecutor Haakan Roswall.
Representatives of the movie, music and video games industry are seeking about 115 million kronor (10.6 million euros) in damages and interest for losses incurred from tens of millions of illegal downloads facilitated by the site.
"It is legal to offer a service that can be used in both a legal and illegal way, according to Swedish law," Mr Samuelsson said at the opening of the trial, which is expected to last three weeks.
He said the site "can be compared to making cars that can be driven faster than the speed limit".
Monique Wadsted, a lawyer representing media firms, including Warner Bros and MGM, involved in the case said: "It's not a political trial, it's not a trial about shutting down a people's library, and it's not a trial that wants to prohibit file-sharing as a technique.
It's not a political trial
"It's a trial that regards four individuals that have conducted a big commercial business making money out of others' file-sharing works, copyright-protected movies, hit music, popular computer games, etc."
The Pirate Bay, which was founded in 2003, directs people to "torrent" links, which allow file-sharing program BitTorrent to download and upload files among potentially millions of users.
Swedish police raided the company's offices several times and seized nearly 200 servers in 2006, temporarily closing the site. But it re-opened a few days later with servers hosted in different countries.
Mr Warg, in a webcast on Sunday, said: "What are they going to do about it? They have already failed to take down the site once. Let them fail again.
"It has a life without us."
John Kennedy, chairman of the International Federation of the Phonographic Industries, representing 1,400 member record companies worldwide, said: "The Pirate Bay has hurt creators of many different kinds of works, from music to film, from books to TV programmes. It has been particularly harmful in distributing copyrighted works prior to their official release.
"This damages sales of music at the most important time of their lifecycle."
Mr Kennedy said the four men had "made substantial amounts of money" from the site, "despite their claim to be only interested in spreading culture for free".
On Sunday, Mr Sunde said: "It does not matter if they require several million (kronor) or one billion. We are not rich and have no money to pay."