[brianwawok]

You don't replace, you use it in addition. Layers of security.

Now if you want to spam 500 million credit cards on my system, you are going to need to at least make them from some common domains, which I can block down the road. If you are using an email hiding service, way easier for you.

Not sure bitcoin matters, if I had users paying with bitcoin in an app I would STILL blacklist certain email domains.