including full package source code in the debian release
Debian releases have 25,000 or so packages and don't include the source to them, so to recompile the package you use apt-get to connect to the internet and download the source to one package at a time if you want the source code. I did some calculations to see how much bulk adding the package source code to the debian release would add and using high compression it appears that it would increase the overall release size by less than 1%. Most users won't care or benefit from having the source code to these 25,000 packages included in the distribution, but some will probably like the ability to be able to have this source code and be able to recompile packages without requiring internet access to download package source code.
Here are my calculations, they are rough estimates:
packages included in Debian 4.0 etch (283 million lines of code)
assuming 32KB per 1000 lines of code, this would be about 8.6GB for 283 million lines of code.
assuming a factor of 100 for the compression of this code, this would give approx 88MB of extra space required in the debian distribution for all of this source code.
the total size of the current full Debian distribution is over 18GB:
so including compressed package source code would have a very minor impact on the overall file size of the debian release.