As a scientist, I don't believe regression to the mean exists, it's part of the gamblers fallacy (trust me, I've tested this to see if it's exloitable in real life)
In a random walk system it's actually more common for the value to move away from it's starting value, ie the mean keeps changing. Well, I say more common, I should say just as likely...
I think you might be mixing up your metaphors here, what you're refering to is a boom-bust cycle:
Most games try and avoid this because it is usually deemed as unfun/unfair to lose any money you have made, most games follow an exponential growth curve instead (ever played cookie-clicker? :P)
In my games I instead try and use this to increse the player involvement, but even then, it's not easy. In life the rich always get richer, but mostly because they are smart enough to get that money in the first place, by exploiting this cycle (I made most of my money during the bank recession in 2008, because I invested after their stock price collapsed, it's easy to make money out if a system like this, because unless something collapses, it usually will recover)
Also in the Wayne Rooney case you're talking about player "form" but also the general bell curve of ability an athlete exibhits over time. There's other factors as to why ManU are playing poorly, it's not just to do with Rooney. It's also that other clubs have more money at the moment (like Chelsea, but even they are dwindling)
