There's nothing wrong with curl | sudo bash style setups as long as it's over https and the certificate gets checked.
Even assuming the URL's publisher is trustworthy (which is a poor assumption to make, ever), you forget SSL / HTTPS is broken, that the NSA has established MITM on the entire internet, that your installation process (which should be both versioned and repeatable) now has zero versioning and all the entropy of the network plus bonus entropy.
Even assuming the URL's publisher is trustworthy (which is a poor assumption to make, ever), you forget SSL / HTTPS is broken, that the NSA has established MITM on the entire internet, that your installation process (which should be both versioned and repeatable) now has zero versioning and all the entropy of the network plus bonus entropy.