> There's nothing stopping an artist from selling a work of art as edition 1 of 1, and then a month later "minting" another copy or 10.
There is a social cost to making a promise and breaking it.
> What happens if someone steals someone else's work, mints an NFT and sells it, and the buyer finds out the next day?
Don't buy from random sources. You have similar problems with Pokemon cards, for example. Lots of fakes and it's often hard to tell a fake. However, people have found ways around the issue.
> You still have to verify that what you're buying is legitimate
That it is challenging to evaluate the legitimacy of a seller with a potentially obfuscated identity living who-knows-where is the reason middlemen are inevitable. Even with blockchains.
There is a social cost to making a promise and breaking it.
> What happens if someone steals someone else's work, mints an NFT and sells it, and the buyer finds out the next day?
Don't buy from random sources. You have similar problems with Pokemon cards, for example. Lots of fakes and it's often hard to tell a fake. However, people have found ways around the issue.