By globals, I mean global resources outside of the codes namespace. It may not even be a resource in the process, such as a log file or temporary directory or a database. If you have two versions of a crate in their completely separate worlds, and call both of their init_logging() functions to log to a file specified by an environment variable, things are likely to go pear shaped when they stomp over each others log file.

I'm a Rust novice, but the example I tripped over in Go was https://github.com/golang/glog. It has a module level init() initialization routine that makes calls to the stdlib flags package, manipulating the default command line flags (a global resource). If you ended up with multiple versions of glog via transient dependencies, your program would panic on startup as the second version's init() would make calls only allowed to be called once. Rust thankfully avoids this particular one by requiring initialization to be called by main() (apart from the hack described in the article).