Although it should perhaps be noted, they aren't packaged as they are in Linux, right? Apps generally ship their own copies of libraries inside of the app bundle, and it's perfectly common to have multiple copies of a library as a result. I'm sure I have at least ten versions of the Sparkle framework for instance!

This conveniently avoids most of the downsides of dynamic linking, except I don't think you get any of the upsides, either—which is to say I'm not sure what the point is. I kind of like it because, since I don't mind breaking code signatures, I can replace the frameworks in third party apps with updated copies. But I'm pretty sure that's not Apple's intended use!