Historically, "Hellfire Clubs" were meeting places for upper class persons of a jaunty or disreputable quality, primarily in Britain. In addition to gentlemanly talks of politics, philosophy and business the clubs would also engage in blasphemy, satire and "immoral acts" - the intention being to shock or scandalize the public rather than proper impropriety. Others were directly engaged in acts would be seen as improper by wider society - pagan rituals, wenching, drinking and gluttony, with one organization famously having the motto "Do what thou wilt". Social clubs under the name of "Hellfire Clubs" have persisted in some places such as Ireland into the modern era.
The landscape of many parts of the Solar System is ripe for the resurgence of such social clubs, particularly in cities on Venus and Mars with strong enclaves of European descent and a high-class populace. The growth of social media and life transparency means that engaging in anti-social or "inappropriate" behaviors can tend to catch up with one quickly, which can mean the end of a career (or a very frustrating setback) for many a young socialite. Additionally, class divides are strong, which can fuel a resentment of the upper crust and drive them to private meeting using their powerful resources. But also, hedonism is popular in many areas, especially due to transhuman resiliency. Food, drink, drugs and sex are all relatively harmless to those with a proper morph and medical care - and worst comes can be easily sidestepped by resleeving. While some of the oligarchy are said to have "Immortality Blues" and have grown tired of many normal pastimes, the hyperelite youth of the Glitterati and other cultures are still amused by the "normal" things, and may desire private outlets.
And of course, the intellectual situation is also ideal - Religion is not as common in these regions in AF 10, and many prominent religious groups are known for their current or classic conservatism - making them ideal for parody. Earth nostalgia and "retro" qualities for many classic fashions recorded from the past couple centuries has arisen, though obviously distorted by time, and many "updated" to fit in with modern technology.
Hellfire Clubs follow many similar internal structures. They meet in restaurants, bars or other social venues, or at members homes. All members are treated as equals, and many may enforce anonymity or lack of Mesh access to prevent leaks and recordings from getting out. Men and women may join, a bit of useful historical accuracy, though depending on "authenticity" all members may still be referred to as "Brother". Meetings tend to be regular, such as weekly or monthly, at appointed times, though to prevent gossip journos from getting a handle on them they especially skilled Clubs may rotate or encrypt scheduling. Membership tends to be invite only, with new members being vouched for by a previous one - and many involve hazing or initiation rituals. Hellfire Clubs may even be virtual instead of physical - though this is not as common due to it's lack of apparent "authenticity". Particularly unscrupulous clubs may also operate by garnering the assistance of local criminal elements to hide or help provide "entertainment".
The actual subject of the club varies widely depending on individual social groupings. Some are simple social clubs with an air of secrecy, a place for people of similar minds or ages to gather and speak about topics without public perception, politics, money or social standing to directly interfere. Many are more in a vein of clubs to party and have fun - where exquisite food, drink and pleasures of the flesh are offered. They may also engage in acts of satire or parody, mockeries of religious rituals of elaborate pagan natures or in blatant misrepresentation of classical Abrahamic religion. Others may engage in political satire, skits or other amusements of a more intellectual nature - or just humble pranks. The most extreme and private clubs engage in acts which are not just socially unacceptable, but illegal: cannibalism, snuff, bloodsports, human or animal sacrifice, bestiality, torture and many others - and these are most likely to be connected to serious criminal outfits.
While some regard the Clubs as unsavory, immoral, in poor taste or "wasting time", only the most extreme are seen as harmful or dangerous - and even then the hyperelite who move in these circles may not even care for harm done to "lower classes", though public image in places like Morningstar and the Consortium mean that legal action may still be taken if the word gets out. Some Autonomist groups, such as many militant Anarchists, see the Clubs (and the obscured rumors of them on the Mesh) as exploitative, abusive and endemic of hierarchical systems - but Extropian and Scum clades are generally more approachable on the subject of "do what you will". There are even rumors that groups on Titan, such as the oligarhov counterculture, are interested in similar concepts to engage in socially unacceptable behaviors away from the sometimes oppressive transparency of normal Commonwealth life.