Don't see that anyone's directly pointed to the actual Complaint:
http://www.prnewschannel.com/pdf/Amazon_Complaint.pdf
The part of the complaint that intrigues me is the one involving "trespass to chattels."
http://ilt.eff.org/index.php/Trespass_to_Chattels
I'm not knowledgable about remedies to trespass to chattels, but I wouldn't be surprised to learn that the normal remedy is return of the property, if it still exists. So deep down in this complaint is the issue of exactly who owns an infringing copy of a copyrighted work. But there also seems to be a question about what exactly the property consists of - that is, what, if anything, Amazon actually sold to the user/buyers.
The complaintants have to come in & say "Amazon sold me the ebook and it's mine." Amazon's line of defense is (a) it wasn't a sale, but a lease under which we had the right to retrieve improperly conveyed property and (b) if it was a sale, we didn't have the right to sell it to you so you can't actually own it. I think that the court will easily knock out the second defense, on the basis that Amazon can't be allowed to claim that its own malfeasance is a defense to its actions.
So that leaves us with (a). I don't think Amazon will want to wade into thost muddy waters. Anticipate a hefty settlement.