First, let me say that I'm against Google on this issue, because I do think they are making money off of someone else's work. Work which they have not licensed, not paid for. Google is the largest copyright infringer on the planet, and they do so with great gusto, being very proud of that fact. And people blindly support them, quite emphatically, as if they're not out to take over the world.
That aside, Google (and YouTube's operators before they were acquired by Google) have had to spend considerable attorney's fees defending themselves in this case. Now this plaintiff decides to just drop the case and join another case against them. So now the process starts all over again. It sure does seem like a good way to bleed a company dry, doesn't it? Start litigation, make the company pay, drop the suit, start another suit, make the company pay, drop the suit, start another suit... If a plaintiff drops a case only to start (or join) another one, they should have to pay the defendant's attorney's fees. It's only fair.