Node uses hierarchical dependencies so different dependencies can get their own version of a particular package. I'd agree that this is hardly innovative, but definitely a lot more user friendly than Ruby. npm is great but would agree that attributing Node's popularity to it is unfounded.
It's a blessing and a curse. When a package is tied to a buggy version of a dependency, it's not a lot of fun to try to get the upgraded version in without either forking your dependencies or trying to get everything fixed upstream.
On the flip side, it is nice when (compared to ruby) you have two dependencies that depend on incompatible versions of the same library.
