Since the registry is public, it would be very easy to write tools like a browser extension that would handle validating against the registry, preventing the ty

Since the registry is public, it would be very easy to write tools like a browser extension that would handle validating against the registry, preventing the type of fraud you're talking about. More generally, there's an interesting project called MetaCert that is doing just that (fraud/phishing prevention) using their own cryptoeconomic incentive system.