I doubt it will ever become beneficial to everybody, because one man's gain is always another's loss (just like in basketball, one man's charge is another man's block, unless the player is Dwyane Wade, and then it's always a block. I'm still bitter, by the way. But I digress). However, generally i think it would be beneficial to the human race.

That being said, the only government that would work under such circumstances (global government) is an absolute dictatorship. There's no other way. If you have a democracy, there are so many clashing ideals that no conclusion would ever be reached in your Congress/Kremlin/Parliament/Reichstag/etc. If you have communism, the enormous scale of people to take care of would be unfeasible. But with a dictatorship, power is vested into one man (or woman) who makes decisions and does not go back on them, for the better or worse. Indecisiveness is the worst disease of all. This way you have a ruler who will make sure everything runs smoothly (or who will at least make sure everything is running at all).

Of course there is always the danger of a corrupt dictator (this fear is fueled by past experiences with people like Hitler). But that's the price you pay for a working global government. As the great Hobbes once said, for there to exist a sovereignity at all, the sovereign must be absolute.

And for you anarchists....sorry, it's just not going to work...

Cheers!