Not to excuse the error, but one can argue that at least it was just names and emails and not something more sensitive. For the best part unscrupulous firms you

Not to excuse the error, but one can argue that at least it was just names and emails and not something more sensitive. For the best part unscrupulous firms you've signed up to at one point or another have already sold that email on to dozens of third party marketing firms. Or it's been leaked by others that haven't taken steps to protect their data. Or otherwise the company requesting your email has taken the liberty of spamming it with unrelated guff you're probably not interested in (music industry mailing lists are great for this). The only real protection against it is to keep cycling your email address so the old ones become invalid (to you at least). It's an odd mistake to have been made though, but without the details of that it's pointless to make assumptions about their system.