After centuries of modern medicine, a blood-borne retro-virus evolves to disperse itself through blood transfusions. It does so by a subtle hijacking of its victims' minds.

• Infected become prone to fits of altruism - and enjoy a perverse thrill from donating blood
  
• Blood-banks swell to capacity, buffering your population against a variety of disasters
  
• The prudent player will opt to destroy all stored blood to contain the pandemic

Left unchecked, a counter-culture of 'Militant Altruism' develops around the disease:

• Activists covertly infect the private blood-stores of the wealthy.
  
• The economy begins to fray as infected industrialists abandon profit-motive - in favour of giving away huge sums money in pursuit of ecstatic highs.
  
• As wealth is decentralised, the Stock-market experiences a sustained series of crashes.

Laws can be enacted to safeguard the Public Order against the Public Good:

• Charities and NGOs are banned outright.
  
• Residents are encouraged to inform on neighbours who are unjustifiably friendly or helpful.
  
• Parents must lodge annual expense claims against their children.

Unchecked effects of 'Selfish Altruism' threaten natural market forces:

• NGOs adopt hit-and-run guerrilla tactics to deliver their services
  
• Charity shop ladies, jailed as black-marketeers, are freed during the 'Friendly Rots'
  
• The 'rogue charity worker' becomes the new bad-ass anti-hero celebrated in pop-culture, finally displacing the much admired gangster archetype.

If the madness is allowed to continue:

• Essential goods & services are distributed according to need instead of profit
  
• Money becomes devalued as a means of exchange
  
• Francis Fookuyama publishes his sequel: "The End of History, and this time I really mean it"

The last three remaining billionaires fill their rockets with worthless paper. They flee Earth for a dome on Mars, furnished with a single poker table and three chairs. A tragic loss to Humanity.