- Confirm that this (or any of the dumps) is the data. This almost definitely opens them up to lawsuits coming from a bunch of people who have little to lose. I say "little to lose" because a non-trivial number will be on the verge of divorce about to lose half of everything.
- Keep their mouths shut and confirm/deny nothing. The press will continue on the story until they're bored and move along but that could be a long time because of the names and information involved.
- Deny that this (or any of the dumps) is the data. All they have to do is keep planting the seed of doubt and some portion of the press will hesitate publishing names because they don't want to look like idiots and/or open themselves up to lawsuits. Because of course anyone with an axe to grind will make sure their opponent (or boss or whatever) is listed in one of the dumps to target them. Further, this shields some of their customers and gives those customers' divorce attorney's a "plausible" scenario to fight against.
All of that said, I wonder if there's some way to validate some of the accounts with the site. If you can do that with some of the leaked data, you may be able to prove that some portion of the data set is real..