[jazzyjackson]

> there's no telling which fork of the blockchain wins

That's the point of proof of work: longest chain wins.

Yes in a netsplit you can spend on both chains, but you would need access to both chains to do so. And you don't even ever have to merge them again, there could just be AmericanBTC and RussianBTC from here on out.

[rhn_mk1]

The problem with keeping them separate is that there's no singular "you" who decides; there's no telling what will happen, causing an inherent uncertainty.