I've heard of it. There is a lot of controversy about what is really happening. We all know that small amounts of powder in large cases can cause erratic ignition and burn patterns. I've seen articles on the impact of powder positioning on velocity, with tests done by pointing a revolver skyward first to allow the powder to settle back against the primer for some shots, and pointing it downward before firing to get the powder up against the bullet. The upshot (pardon the pun) of it all is that you don't get good accuracy when the powder can move around a lot, because you introduce too much variability.
There are also reports of light loads detonating instead of burning, and causing guns to blow up in the process. I read an article online a year or so ago in which the author claimed to have blown up a T/C Contender with a very light load. As you probably know, smokeless (nitro) powders are classified as "propellants" not explosives. They are supposed to burn, not detonate (explode). Some people believe that under the right conditions, a small amount of a nitro propellant in a large case can actually detonate, much like a dust explosion in a grain elevator.
As I understand it, however, there is a lot skepticism about these claims. No one has been able to make it happen under controlled conditions (in other words, "on purpose"). The skeptics believe that most of the reported incidents are actually the result of double charges, which of course can easily happen with small quantities of a fast powder in a very large case. The skeptics point out that the people reporting these incidents have no way to prove that the loads weren't double charged, and that they have a vested interest in claiming they weren't, i.e., they'd rather blame a freak phenomenon than admit they screwed up loading the round.
I don't know what to believe. I'm a skeptic by nature, though, so I tend to think that until someone can replicate such a detonation under controlled conditions, it's more likely myth than fact. Still, I am a careful reloader. I load some big ole black powder era cases (.45-70, for instance), and sometimes use smokeyless propellants. I am very careful to inspect each case, and stick to minimum safe loads listed in published reloading manuals.