In the latest case, as the Electronic Frontier Foundation explains, Sony has sued computer security researchers:
for publishing information about security holes in Sony’s PlayStation 3. At first glance, it's hard to see why Sony is bothering — after all, the research was presented three weeks ago at the Chaos Communication Congress and promptly circulated around the world. The security flaws discovered by the researchers allow users to run Linux on their machines again — something Sony used to support but recently started trying to prevent. Paying lawyers to try to put the cat back in the bag is just throwing good money after bad. And even if they won — we'll save the legal analysis for another post — the defendants seem unlikely to be able to pay significant damages. So what's the point?