The way I see it, we're headed towards one in all but name. Treaties are basically the sharing of laws at the end of the day, sure we negotiate them as financial reasoning, but they usually end up leading to laws such as forcing the DMCA or the Kyoto Protocol that require member governments to conform to certain standards, almost always those standards are done via law. We can say these are being done in mutual interest, but at some point we will be a group of countries following a standard set of laws, I'm not saying anytime soon or that there won't be resistance, but one day it's a vast possibility. Instead of indefinite treaties we should use mutual agreements for set periods, at the end renegotiate them. Of course this could just be the ramblings of a mad man who has no clue. Also this doesn't necessarily mean a one world government.
I think a "government" like the UN might work fairly well. I don't think that something like the US federal government will ever work too well on a government scale. A world government has to somehow manage both the middle east and the whole area around sweeden (can't remember the name). It would have to be a very "soft" government that enforces very few things, and works to prevent and shut down any war. Also, how would it manage when two nations have conflicts with one another. Those boundaries aren't going to disappear, and while US states can get along well, no two states are really in competition with each other as countries are. Or are they? I have never heard of the possibility of two US states being in a condition where they would go to war (civil war aside)
I think it would work. It is kind of a broad question - many states that are bad places work. I don't think that a world governments would be desirable. It seems that it would create a power structure with an incredible potential for abuse. If we are to have governments, it is best that they are small and fragmented. At least this way some may be able to provide a safe haven, or a check on unrestrained power. For example, if a state becomes abusive its people may flee elsewhere. If the entire world were one state you're basically stuck with what you have got. This is already a problem due to immigration laws and borders, but it would be absolute in a single worldwide government. I also feel like there are many communities who might want to live in very different ways. A local community may be able to agree and live in harmony with social rules and mores. But if we tried to apply one standard of law to the entire world I think many people would not be content with laws.
No. Unequivocally: no. Governments have problems already due to the fact they try to make global laws which affect too many people in a negative way i.e. there's too many doubtful cases who are affected negatively by a law and cannot get repairs. The centralization of power will lead to corruption (even more than nowadays), since the power will eventually rest with a handful deciding for the rest. Apart from being against government for principal reasons, IF you want a government: keep it local and decentralized.