I am a packager for Fedora and I have one package which has been up for review for the past six month. The main reason why it is so slow is that the package bundles a few libraries. So for me the Fedora policy is annoying, but I am still convinced that it is the right way.
At the moment I see the distributions as the only voice which stops the bundling of libraries. And with this they also reduce the number of forks for these libraries. For an application developer it is always easier to bundle libraries and patch them up to fit the needs of the library instead of fighting for these changes with upstream.
This will slow down the development of the libraries and also reduce the quality. And once this happens the applications will have nothing left to bundle.
In my opinion one reason why open source is so good is the reuse and improvement of the libraries all the applications are using.
And once libraries get bundled, what will stop the bundling of applications. It might make sense for Firefox or OpenOffice to bundle stuff like MySQL, Gimp, ImageMagick or maybe sshd in slightly changed and "improved" versions.
And then there are still the already mentioned disk space, memory usage and security problems.