> The first advantage to just copy-pasting is that the snippet author might update it (e.g. if he finds a faster/safer way to do the one thing his package does), and you don't have to do anything.

First, please don't copy paste solutions. Understand them and implement correctly. Stackoverflow is not a magic library you should take books from without understanding.

> Imagine finding a solution on Stackoverflow and just being able to import foo from stackoverflow/a/12345, and when the community finds a better way to do it, your software is automatically using the new version!

Wow, I've just imagined it. Props for the great horror story, but... it's a security nightmare. You basically surrender all control over your project for almost nothing.

> The second advantage is that it's basically built-in refactoring: Code from these micropackages will not litter your code, there is a clean separation between what is your business logic vs where you just need some generic functionality.

Writing this utility in a separate code unit (namespace, project, whatever) gives exactly the same advantage. And micropackages will litter my building process / dependency tree.