No. It is not. I'm really tired of this argument. It assumes other platforms are the same as Linux, and that's incorrect.

Here's why you're wrong:

Unlike Linux, Mac OS X ships with a standard, stable, and exceptionally complete set of libraries. Apple goes to great lengths to maintain binary and API compatibility, and this means a few things:

- Most applications will only require Apple-supplied libraries, as there's very little that isn't provided by the OS libraries.

- Apple keeps the OS libraries up-to-date.

This feature-complete ABI/API-stable environment is not free for Apple to provide -- it takes a lot of effort to provide a consistent API across libraries and maintain the API/ABI compatibility across releases, but the advantages are tremendous. Mac OS X has been able to skate by without package management for years because this approach allows for drag-install drag-uninstall application distribution.

UNIX derivatives, on the other hand, were faced with a lack of standardization of core application libraries, a huge number of incompatible libraries to fill in the gaps, and a software distribution model that involves splatting files all over the disk. The end result is that you need a packaging system to maintain security updates, manage all the files on disk, and upgrade the world in lockstep due to API/ABI compatibility issues across libraries shared by wildly disparate applications.

So -- tl;dr -- it's not a security 'nightmare' because the core libraries that everyone uses are already shared and updated by the OS vendor.

This is also what makes Mac OS X so much nicer to develop and distribute applications for as compared to platforms that require a centralized package manager authority to keep things sane.