Trek's economic system has always been a bit ambiguous. As a result it has been used to advocate pretty much any system of economy. Some people (for example Saab Lofton in the preface to his (terrible) novel A.D.) see the Federation as a perfect example of a traditional left-wing socialist society in which the structures of Government have withered away (a la traditional Marxist thought about the development of a Communist society), others see it as the pinnacle of libertarianism. Personally, I think both are wrong, Star Trek has never really dealt properly with the politics of economy and probably never will, it's far too interested in the touchy-feely stuff (perhaps Gene Roddenberry decided to be as cautious about Economics as he was with religion in Star Trek).

A much, much better treatment of Economics in an SF context is demonstrated in Iain M. Banks's Culture novels, and his own essay "A Few Notes On The Culture" discusses the issues in much greater depth. The universe of the Culture is a similarly space-faring technophiliac utopia, but (perhaps due to Banks' left-wing Scottish upbringing) isn't afraid to deal with the obvious consequences of such acheivements.