I'll let you know if i hear about a data breach at one of the sites i deleted my account at. But personally, I will think i wont ever know if this is useful or not. But this is a good mindset going forward of being more conscious of where i put my data online and how reveal myself through the use of a email across different sites.

The least i can do is use throw away emails and give them as much false info as i can get away with.

But if you asking how well account deletion works, some will delete everything, but most will just "deactivate" whatever that means. And some still that had money go through them are usually legally required to hold onto something for a number of tax years.

I think doing thisis better than nothing