I just finished reading Look to Windward by Iain M. Banks; it is part of a series about the Culture, a space-faring, post-scarcity, socio-anarchistic utopia watched over by immensely powerful AIs known as Minds that keep the biological inhabitants of their Orbitals or Ships safe and happy. Thanks to nanotechnology almost anything is available to anyone if they want it, most of the Culture's population lives in gigantic Orbitals that can house 50 billion people with room to spare, both of which make it so that no one has to compete with one another for living space or consumables, in fact most citizens simply spend their time playing extreme sports or some other activity they find entertaining instead of working. People don't even have to worry about dying as they can have backups of their consciousnesses made in case they die in a lava-rafting accident (though some choose to be "disposable" as a lifestyle choice).
Despite all of that the Culture isn't a perfect society by any means, for one thing they have an annoying tendency to interfere in the cultures of other societies that occasionally results in war. A major part of the plot of Look to Windward is a civil war that the Culture unintentionally started by attempting to dissolve the caste system on the planet Chel and the Chelgrian's attempt at reprisal by blowing up the Hub Mind of the Masaq Orbital and killing at least 5 billion of it's inhabitants. And after the attempt fails Special Circumstances sends a Terror Weapon (a shape-shifting nanoswarm with a sadistic personality) to gruesomely and publicly assassinate the Chelgrian leaders responsible. The Minds might not all be the benevolent overseers they seem to be, the Masaq Hub speculates that the Chelgrians may have been helped by a renegade group of Minds who believed the Culture had grown too complacent and decadent. In addition multiple alien races considered the Culture to be immature and impulsive, I personally think that the biological citizens are like spoiled children, they don't have to do anything and most contribute nothing to the Culture at all. Plus I doubt that there could truly be a post-scarcity society, even if one is able to transmute one element into another through nanotechnology there is a limited amount of matter and energy in the universe, I wouldn't be surprised if the Minds are secretly scheming to overthrow other cultures or to claim one another's resources (which for all we know could include citizens).