Native OS X apps either statically link everything, or shove all of their dynamic libs into a single .app package... that's why their binaries are so big. This avoids shared lib versioning nightmares and makes everything "just work" (including drag-and-drop installs), but it also means you have 30 bajillion copies of libXYZ on your disk.

I would not say this is the norm. If you look at Sandbox-enabled third party applications such as Google Chrome, it is well defined what libraries it dynamically links to outside of the directory it is installed in.