I've been thinking recently about magic and how bad it would be for the world if we had it. And I don't just mean in the typical "Power corrupts and absolute power corrupts absolutely" kind of way, either. More how magic would further the divide between the working and wealthy classes within the setting, help evil magic-users overthrow democracies and install themselves as a dictator or monarch, and how magic would end up being hoarded by the wealthy and/or governments of the world. Magic schools for bards and wizards would be more accessible to the wealthy, and people with innate magic would be more likely to be wealthy (under capitalism, at least). So Sorcerers (and maybe other full-casters) could use their magic to make money, then use that money to send their children to schools/colleges that would teach them magic, which would then create these ultra-wealthy aristocratic families that could then use both their magic and money to gain a ton of political power and control over the world around them (and become even more wealthy, because that's how capitalism works). Magic, under capitalism, would just further the imbalance between classes in the world. And even without capitalism, governments would prioritize recruiting magic users to their organization and would likely only last all that long if they had some control over magic in the first place.
There are already settings that kind of touch on these ideas, like Eberron and Dark Sun, but none really go that deep into it. Magic would be bad for us, at least in our current socioeconomic system. It makes me want to make a new setting revolving around these ideas . . . but I'm already making two new D&D settings. I really probably shouldn't start making a third.