Keysersosa answered this better below, but basically maintainability. There was no writeup, I guess because doing write-ups about internal software switches wasn't really a thing back then. :)

Yeah I think that post dates from a time where you still heard people refer to them as "weblogs".

Edit: Found it. It was the 14th post on our blog a time, but definitely light on the implementation details. http://www.redditblog.com/2005/12/on-lisp.html

Thanks for sharing this post!

About this: ===If Lisp is so great, why did we stop using it? One of the biggest issues was the lack of widely used and tested libraries. Sure, there is a CL library for basically any task, but there is rarely more than one, and often the libraries are not widely used or well documented.===

If Clojure was available back then and if you had written it in Clojure instead of Lisp (and given that Clojure can leverage JVM based libraries) - would you still have continued using Clojure?

I know this is an extremely hypothetical question but I am trying to figure out if Lisp is finally getting ready for "mainstream" adoption because Clojure is bootstrapped of the libraries of Java.

Clojure is a beautiful language and its web ecosystem is improving rapidly, but breadth of, depth of, and support for libraries is still its main weakness next to the likes of rails and django. Clojure's a lot better for solving hard problems, but you'll also spend a lot more time getting tripped up by things that seem like they should be easy and reinventing wheels. Fortunately, it seems a near certainty that this will eventually no longer be true.

I think OP meant a writeup about the switch from web.py to Pylons. I'm not sure we ever wrote that one down.

Point! I think I found it http://www.redditblog.com/2007/08/its-slow-its-unstable-its-...

Also just as anemic as the last one. Oh well.

I dunno; the ending's pretty good.