I learned all I wanna know about class action suits from the novel, King of Torts by John Grisham. Class action lawyers are grabbing for the brass ring. They target big companies, large group settlements (which, by the time it reaches the little guy, could be peanuts), take a percentage off the top for "expenses", and divvy up the rest with those who sign up. They can be very aggressive when they decide to grab up any potential litigants. They want to beat any other lawyers to the big "pot" at the end.
That is, of course, if their suit is legitimate.
Good question. If you don't feel wronged by PayPal, why go after them? It is true, a big settlement can bring a company to it's knees.