I disagree with your thesis; anyone with malicious intent can be assumed to already have their own copy. Even the Adobe dump is under 4gb compressed - a trivial

I disagree with your thesis; anyone with malicious intent can be assumed to already have their own copy. Even the Adobe dump is under 4gb compressed - a trivial amount of storage. Additionally, there is a huge long tail of publicly available user databases that are not included in this site, which along with the lack of hashes makes it worthless for the purpose you envision. It's also extremely easy to tell if an email is registered on a website if you aren't concerned about the victim being notified. You just need to attempt to either reset the password (it'll say whether the email exists) or register a new account with their email.