Although I doubt this is going to make the diehard objectionists feel any better, there are actually pretty strict laws in place surrounding privacy and personal info data protection that eBay has to comply with - above and beyond what they had to do for the basic info they already have, like names, phone numbers, email and postal addresses, plus credit card info for those that had that on file for payment of fees or verifying their account, I mean.   

This doesn't mean it's impossible for it to be compromised, but it should be encrypted and very difficult to make any practical use of.