Many of us who operate our own mail services use a unique email address for every web service we use. You'd be surprised how many of these unique email addresses I've received spam at (and have subsequently blackholed). I would estimate less than 50% of the associated services ever report a data breach event. I figure either there has been an unreported breach or, possibly more likely, the service sold their userlist either directly to spammers or sold it to another group who was themselves breached. The upside, though, is that blackholing an address used for a single service is super simple and satisfying.