[the_third_wave]

Tell me then, how do you enforce the essence of a communist economic system, this being communal ownership of the means of production, without an authority to tell Mr. Smartpants who just invented a better mousetrap that he has to give it to the commune instead of producing it himself?

Nope, Communism is more than just an economic system. It is an ideology which strives to create a "better man" who can create a "better society" where human "vices" like greed and avarice no longer play a role. In this it closely resembles religious orders which strive to create the same through other means.

Capitalism is 'just an economic system' which can be implemented in many ways ranging from laissez-faire libertarian-style capitalism to state capitalism as practised in China. It does not come with the large ideological baggage Communism carries since it doesn't need to - leave people to their own devices and they'll end up doing something resembling a form of capitalism at a large scale while practising something resembling communism at a small - family and neighbourhood - scale. This model works fine since there is no ideological drive to force out the small-scale 'communism' in families and neighbourhoods whereas a communist society needs to do away with the large-scale capitalism. Communism and authoritarianism are indelibly linked.