i assume this is like splitting a stock.. i don't know how it all works, but it'd be for psychological reasons mainly (and plus computation)... so how do they decide when it is a feasible option?

This. Underneath it all, the bitcoin network deals in Satoshis. On the surface, we set our software to display 100000000 Satoshis as 1 Bitcoin just to make the large numbers easier to manage. It's completely relative, like saying $600,000 vs $0.6 Million.

Many gambling sites have already switched. My site will display everything in mBTC. You can choose to refer to it solely as mBTC from now on, that is your choice.

I saw a video of a bald-headed guy today declaring that there's a hundred thousand gazillion bitcoins, an infinite number. Maybe I should have paid attention that day in class when my teacher taught such a thing instead of working on my history homework, incorrectly assuming he was covering a chapter I read three months prior.

Quick aside, related to above. One night, at around 11PM, my mother asked why I was still doing my homework. I told her it wasn't homework and that I was several chapters ahead. She immediately sent me to bed, but unbeknown to her, I was still doing equations in my head up to falling asleep. Damn, I miss school!

Luckily, there weren't any classes on how to become TMIBTCITW, otherwise I would have had competition.