Unfortunately, most of the people getting scammed out of ADA are those who did zero research before sending their ADA. Some people need to learn the hard way that you cannot get something for nothing and there is no such thing as get rich quick. There will always be 5-10% who fall for this.
Having pages set up to warn people only helps protect those who are smart enough to look for more information. So we cannot protect the simpleminded who want to get rich quick without putting in the work or thought.
So how do we protect those who actually look for clarity? I like your idea of the browser plugin or maybe a discord or other chat service. Like many of us, I work from home. So I have the privilege to sit in a chatroom in the background and I could be “activated” to take action if a scammer or fraudulent account or website is discovered.
I do want to stress that I support taking action ONLY against fraudsters and scammers and not people who might be bad mouthing Cardano or have a differing of opinions than our own. Creating a volunteer watchdog collation with clearly defined goals and objectives would be great but isn’t that kind of what the Cardano Foundation is?