Since most users use the same account login and password, getting access to one account can potentially translate into having access to all accounts. Account takeovers are a growing problem. Don't use the same credentials, people. Seriously. Password1 or Qwerty1 is not a safe password. I'm shocked that was still being used in 2013.
Of course it's valuable to criminals.
It's likely that the criminals will use, or sell on the data to hack people's accounts and make illegal purchases.
It will be very costly to Ebay, and very costly to those who don't change their passwords and become subject to fraud.
Even if the data is not sold on or used in such a way, it's a good way to attack the corporation Ebay as it'll cost them money to put it right again.