Elite: Dangerous. A bug caused numerous players to receive a credit "refund" that wound up making them instant billionaires, which might have had some long-term ramifications for anyone who had hoped to actually play in the sandbox economy in the future. While the developers had initially opted against wide-scale rollbacks, asking instead for affected players to choose whether to be rolled back or not, that decision has been reversed.
Unexpected billionaires will find all of their bug-gotten gains rolled back and removed, with the development team contacting those affected personally to make sure that nothing legitimate gets caught in the crossfire. Meanwhile, players who found a way to exploit the game explicitly will also see their gains removed. So those who were hoping for rollbacks in the wake of these issues will be happy; those happy with billions of credits for no real effort will be... less happy.
[Thanks to Cotic for the tip!]