Given that my FM3 had whiteout on it I'm inclined to agree that Mexican FM2s and FM3s are not nearly as secure as other types of ID. Apparently blank FM3s have have been stolen before. So clearly there's a compelling reason to steal them. They seem like they wouldn't be too hard to duplicate, but maybe the mafia has better things to do. Or maybe the paper is impossible to get. Or maybe there are things we haven't noticed that make them more secure than we think. I have no idea. But I know you'd be surprised to learn all of the ways that agents detect fake docs, there's a lot that goes into it. And when people are entering the country with ill-gotten documents they don't act normal, even if they think they do. People, especially desperate immigrants, are nervous and can't help it. Agents don't just look at the documents, they look at the people. If something feels off then they send people to the office for further revision. And unless you've been trained by the CIA there's a high chance that you are a bad liar and will screw up and get caught lying. INM trains agents to detect lying and they train them the art of interrogation. Most people don't stand a chance against people who are that experienced with this stuff. So even if the document is real, if it's ill-gotten there's a high chance that the agents will figure out that something isn't right.