Happens every day in the US. Mostly video and music (MPA/RIAA). There's also been some effort put into extorting ISPs for the activities of their customers, but the effectiveness of that is still being determined as cases work their way through the court system. We should have a better idea this summer after the supreme court decides on the $1 billion in damages one ISP was ordered to pay to a bunch of RIAA labels.

It will be a lot more profitable to sue ISPs than it is to try to sue poor parents and grandparents for what children do online.