Not to fret. Getting sued is no big deal any more. This is more a publicity stunt than anything else. There's been enough legal precedent in court cases that the 'safe harbor' provisions protecting web hosts has been prerty well established by now. I doubt it will go to full trial. And if it does, it won't go anywhere. The real target is Limewire. All the other co-defendants are in there just for show, and maybe with the hopes they'll gang up on Limewire and try to cut some sort of deal with the plaintiff. Dint hold your breath for that one either.
In the United State, anybody can file a lawsuit at any time for any reason. As long as the necessary paperwork and filing fees are received, it will be placed on the docket. The court's clerks (by law) are not allowed to exercise any judicial review of a filing. That's for a judge to decide once it goes to an initial hearing in court.
Many stupid and frivolous cases are summarily dismissed without going to trial by the judge who gets the case. Occasionally one makes it through if the governing laws are vague, or if there are extraordinary factor in the case such that a judge feels it necessary for the court to weigh in on. And the courts are busy enough that they tend not to suffer fools gladly.
The real problem is the useless attorney who files because he's been asked to even though he's totally ignorant of the relevant law or the legal precedents for a suit he's filing. Even worse are the ones who knowingly bring a lawsuit they know has no legal merit. These are the parties most responsible for clogging up the court docket. And as long as 'frivolous' filing is dealt with so leniently, there's little downside to going in with a bogus lawsuit.
Either way, the attorney gets paid. And the press sends in some coverage.
And that's what it's really all about.