For what it's worth, a MUD is where I learned to code. In my case, it was an LP MUD (LP, short for LPC, short for Lars Pensjö C (if you're reading this, Lars, <i>Thanks!</i>)- the language in which it was written).
MUDs were an <i>excellent</i> place to learn programming. Getting tangible results from just a few lines of code was a great motivator.<p>"I want to code an orc!" Sure, inherit the right class (monster), set a name, a description, and a few other attributes, and clone (instantiate) the guy. There's now an orc standing in front of you!<p>"I want my orc to wield an axe!" Sure, inherit the right class (weapon), set a name, a description, a few other attributes, and clone the axe. Give it to the orc, and have him wield it, by calling the wield() function with the online debug tool that was part of the game world.<p>All the while, being surrounded by dozens of helpful people who would answer my silly newbie questions and review my code. And there was <i>plenty</i> of example code to look at. Granted, most of it was perhaps examples of <i>bad</i> ways to solve problems - because it was written by other beginners, but examples to learn from none the less.<p>My participation in the MUD directly lead to my first programming job, and taught me <i>tonnes</i> about programming in general, and - heh - debugging other people's code in particular.<p>MUDs really changed my life, and I have several friends with a story similar to mine. You can't overstate how important they've been to many.