I've recently read The Sparrow and Children of God , by Mary Doria Russell, both of which I quite enjoyed, and one of which featured an interesting scam (the following is not a spoiler, in any meaningful way).
One of the more nefarious characters, before he found his way into the plot, made a living by locating terminally ill rich people and convincing them that, if they left him their estate, he'd put them onto a relativistic hospital space ship. This would cause their subjective time to pass substantially more slowly than that of people, and medical researchers, on Earth. Eventually science would catch up with the problems his patients faced, and they would then end their high speed journey and be cured.
Of course, this being a scam, the patients were simply flown around at normal speeds, and so died pretty quickly, leaving our anti-hero with a fat pot of cash for his troubles.
Now, this leads me to wonder if one could create a protocol that would allow a suspicious trust fund on Earth to be certain that a clock on a fast moving ship was actually moving fast, and not simply sitting around not doing much. It wouldn't be enough to broadcast some physical thing happening, as that could be tampered with.
Also, following other news I propose a project to calculate busy beaver numbers. It could have a slogan: "Beavers for Hubris".