...which means a login is now tied to a browser, and you have to come up with a way to securely export or sync private key (bad idea?) or a way to link another

...which means a login is now tied to a browser, and you have to come up with a way to securely export or sync private key (bad idea?) or a way to link another browser to a login. Also user losing access to all their websites by accidentally uninstalling a browser doesn't sounds very user friendly.