I'm not of the faith that says that p2p or crypto currencies are necessarily a good thing. I, personally, think it's a good thing that democratic governments can exert control over fiat currency in order to attempt to mitigate economic disasters. I certainly don't think that the (for example) bitcoin model is a good one.
>> and encrypting their communications
I'm not really sure what this has to do with governments or control. I don't think democratic social order necessarily depends upon being able to surveil everyone, it's just a trap that the current bunch have fallen into.
>> production structure not suffering from possibility of monopolism
I'm not really sure what you mean here either, but it's hard to forsee a state in which monopolies are somehow impossible, or how the lack of them would imply the lack of need for government.
>> how will the government exercise their control?
In much the same way they do now, by the majority of us granting a democratic government a monopoly on the use of force. I'm not sure what bearing the form of currency, or encrypted comms, or even a utopian ideal of monopolistic impossibility have on this.
--edit-- Please do not take this as me saying either that I think the way governments have handled currency is good, or the way they do ... pretty much anything is all totally awesome. Far from it.
--edit 2-- The use of language is interesting here. Correct me if I'm wrong, but you see government as the external imposition of control on to otherwise free citizens? I see it as (at its best) free citizens banding together to achieve collective goals and prevent the worst of human nature overtaking us. The rhetoric and the social measures that come from government in this day and age are pretty abhorrent, but collective defence, roadbuilding, education etc are (to me) vital and useful functions.