I maintain that without the legal fiction of a company they could not. Companies are not real things, they are legal fictions.
They externalize cost, through government, without government they could not function more efficiently.
If you've ever been involved in a co-op, they tend to operate extremely inefficiently.
If you're arguing that corporations as we know them would not exist without government, I completely agree with you. Subsidized security is the best thing the state has to offer the mega corporation. The more geographically dispersed resources you have, the more benefit you gain from having the state protect those resources, versus if you had to explicitly pay to have them protected. That said, if there were no state, I don't think the world would turn into an anarcho-socialist commune. I think you would see the large corporations dissolve or break up into smaller businesses, some of which might be run by the workers.
Babylon, gene...
It seemed earlier like you guys were arguing for the state, now it seems like you're arguing against it, and for something like anarcho-socialism. If that is the case, why are we arguing? We both agree that society would be better served without a state. The only difference is that you think the best society is one where there is no private ownership of property (MoP), whereas we do. If you try to enforce your opinion on how society should form lacking a state, how are you acting any differently than the state itself? Lacking states, there will be more than enough room in this world for all sorts of different voluntary organizations of society.
Different sorts of Anarchists often seem to be arguing for a state when debating since we have different ideas as to what constitutes bad power.
The main reason that, IMO, Capitalist and Socialist anarchists need to keep debating is that I doubt that corporations would simply wither away if the framework of government were removed. Yes, a Democratic government is far from an ideal solution, and yes the corporations do capture it and use it to enrich themselves. However it is still preferable to the corporations ruling directly, which is what will happen if they are left in possession of all the resources that they currently possess without the government to keep them in line.
I have no problem with market anarchists, in fact I am one, as are many of you who label yourself capitalist, but as long as there is support for ownership of capital determining production, rather than actual use of production determining production then there is support for government.
I guess it's true what they say about great minds and all that.. 
