Abhishek Jain asks Stack Overflow about the differences between zlib, gzip and Zip, and gets a fascinating and very insightful response from none other than Mark Adler. I particularly like the comment Adler made when the OP asked about referenecs for his answer. I am the reference, having been part of all of that. This post could be cited in Wikipedia as an original source. This, to me, is a perfect example of the enormous impact of open source and free software libraries developed in the 80s and 90s have on modern-day computing.
I like auto-fill-mode and even have it customized for LaTeX-mode in my Emacs configuration. However, while working with other people via a distributed version control system, like I do with my friends, auto-fill-mode can be a real pain if not everyone uses it. Whenever the ones that do commit any code, others are annoyed because it’s difficult to see the changes in the diff file, since auto-fill-mode reformats paragraphs (hence producing ‘more’ changes).