By Robert Plummer
Business reporter, BBC News
Five years ago, the US music industry prosecuted a 12-year-old girl for illegally downloading songs. But now, even toddlers are facing the wrath of record company lawyers.
Prince likes to exercise control over how his music is used
In one of the strangest copyright infringement cases to come before a judge, a mother is fighting for the right to post a video on the internet showing her young son dancing to a song by Prince.
Stephanie Lenz uploaded the 29-second clip to YouTube in February 2007, but it was removed from the site four months later after objections from Universal Music Publishing.
Ms Lenz successfully applied to have the video reinstated, kicking off a lengthy legal battle that is still playing out in the federal courts in California.
Universal's lawyers probably hoped that they could quietly remove the video from circulation. If so, they will doubtless be dismayed at just how counter-productive their efforts have been.
Publicity for the case has boosted the appeal of the clip, which has now been viewed more than 593,000 times.
Anyone looking to download an illegal copy of Prince's hit song Let's Go Crazy would not be happy with the poor sound quality of the brief snippet used in the Lenz family video.
As the record's guitar solo plays in the background, the unnamed tiny tot bounces up and down in time to the music while holding on to a toy pushchair.
"What do you think of the music?" asks the boy's mother as he grins.
Universal tried to block the resale of promo albums
Ms Lenz says she posted the video so that her friends and family could see her son's dancing.
But the footage drew objections - not from Warner Music, which owns the recording itself, but from Universal Music Publishing, which has the rights to publish the song.
Universal, of course, has already been on the losing end of another high-profile US court battle over copyright this year.
In June, a judge quashed Universal's efforts to stop an eBay trader, Troy Augusto, from re-selling promotional CDs he had bought from second-hand stores.
The company had accused Mr Augusto of copyright infringement, saying the promotional items were not for sale to the public.
In this latest case, Universal argues that it was entitled to send YouTube a takedown notice under the Digital Millennium Copyright Act, because the use of Prince's material was "not authorised by the copyright owner".
But Ms Lenz, backed by digital rights lobby group the Electronic Frontier Foundation, is seeking a judgement that the video is covered by "fair use" provisions in copyright law, as well as unspecified damages.
"Because Universal's notice was intimidating, Ms Lenz is now fearful that someone might construe some portion of a new home video to infringe a copyright," her complaint states.
Brianna LaHara was one of the first people to be sued for file-sharing
"As a result, she has not posted a single video on YouTube since she received the takedown notice."
Last month, US District Judge Jeremy Fogel rejected an attempt by Universal to have her case dismissed, saying that she had incurred costs in fighting the action, although the exact nature of any damages was yet to be determined.
Until this saga came to light, the youngest person involved in a US music copyright infringement case was 12-year-old Brianna LaHara, of New York, who was one of 261 people served with a lawsuit by the Recording Industry of America (RIAA) in September 2003.
She admitted swapping music online and her mother agreed to pay $2,000 (£1,257) to settle the case.
Where Miss LaHara was concerned, the music industry could plausibly argue that she had downloaded music for nothing that she would otherwise have had to pay for.
But no-one could reasonably maintain that Ms Lenz's lo-tech, lo-fi home video had dented sales of Prince's music. So why did Universal's lawyers try so hard to suppress it?
The answer probably lies in Prince's own hard-headed attitude to commerce. As the music industry undergoes rapid change, the diminutive star has done his bit to reinvent the standard business model of popular music.
Andrew Bain has fallen foul of Prince's obsession with control
His recent innovations have included giving away his Planet Earth album in the UK with copies of the Mail On Sunday newspaper, using it as a promotional tool to boost interest in his live performances.
But at the same time, he has a well-known obsession with preventing people from using his music in ways that do not meet his approval.
After playing a run of 21 sold-out gigs at London's O2 Arena last year, Prince hired UK firm Web Sheriff to make sure that no grainy mobile-phone clips of the concerts could be found on YouTube.
More recently, Andrew Bain, a north London dentist, secured a recording contract with Sony BMG on the strength of his operatic pop version of Prince's Purple Rain, but was then told that the song's creator did not like his rendition and would not allow him to release it.
In her complaints, as outlined in court papers, Ms Lenz describes Prince as "notorious for his efforts to control all uses of his material on and off the internet".
"[Ms] Lenz alleges that Universal is a sophisticated corporation familiar with copyright actions, and that rather than acting in good faith, Universal acted solely to satisfy Prince," her complaint states.
For Prince, this kind of control is "a matter of principle", as Universal acknowledges. For Ms Lenz and the Electronic Frontier Foundation, it's a "bogus" copyright claim. Deciding who is right will be a great deal harder than child's play for the US courts.