I agree in general with what SmartScreen tries to do. There are a lot of non-technical folks clicking on stuff willy-nilly so adding barriers to prevent spyware / virus infections for totally unknown binaries is a good thing.
A "Let's Encrypt" for code signing may be a good idea, but the cost of a certificate is itself a barrier for spyware distributors, so i'm conflicted on that... not sure what the right fix is.