Hey venam that's interesting. But it's also quite obvious, no? In the future someone may name is package "alex-backup" and use the user alex for that.

Good programs/packages/libraries make the user customizeable. (using a configfile or env-variable)

One way this could be prevented would be an installation check in the package to install, if the user already exists it should abort. This is again depending on how well the package is made.