Well, just like what Picard said in the Star Trek "First Contact", that we don't have money in 24th century. But, is it possible in real life in a very advanced civilization like we are today or beyond? Ok, maybe there is no money, but no currency system at all? Is it possible? Because : 1. Without money, what is the stimulation for people to establish private companies? Work for free? Oh common, we are human not an android. Without money, there is no urge to become rich, so I suspect that there is no private company in 24th century (Star Trek world). 2. There are two types of humans in this universe. The diligent and the lazy one. So... say you are a diligent human, work hard for the Federation, and I'm a lazy human who love only masturbate myself in a holodeck. So..., without currency system, how could the diligent keep diligent, while the lazy get whipped to work? What is the reward system in the 24th century? If I can take everything without to do anything why should I work? A social work? Not everybody will do it unfortunately. 3. And what about private property? Like house, food, shirt, or maybe private holodeck, private replicator, and maybe a private starship, etc? I found that Picard's brother has a farm in France and Sisko's father has a restaurant, is it given by the government or what? And what is the privilege for Sisko father to live in his restaurant? Why not me, not you, or other people? If it is given and free, everyone has the right to take it. So why should Picard's brother or Sisko's father? 4. And what about food? you get rationing or you can get everything as you like without limitation? Say, even with replicator, they need energy, and we know that energy is not free in 24th century. They still need resource. And the government must take it from another planet (there is no Dilithium Crystal in Earth. They must imported it from other planet, and even if it's free, it needs a lot of work to bring it back to Earth). So how could the government prevent the people to waste the energy without any responsibility? Remember there are billion of people in the planet Earth, and everyone need energy to life. And unfortunately, Earth is not the only planet that need energy to life. 5. And what keep people to work? Is it a hobby? Common, how could people work hard for their hobby constantly for the rest of their life? what if his hobby is playing the holodeck game (just playing and he/she is not even bother to make a holo novel program) So either it is rationing, there should be another currency system that being used by the United Federation of Planets. Maybe it is not money, but they have another means to trade. Energy perhaps?