In Sharon's dream world of Harry Barker, "mundane" is a vile insult for a hacker with one or more luddie parents. Elitist hackers use it to imply lesser intelligence and skill, and that mundanes should "just log off, unplug, and never write code again." Despite such "pure-blood" implications, most hackers actually "half-blood" or less.
In "Harry Barker and the Chatroom of Enigmas", the "monster" of the Chat Room of Enigmas, a giant worm, was created specifically to ferret out luddies and mundanes and wipe them from the Internet.
In Harry Potter, the equivalent of "mundane" would be "mudblood". This parallel is also echoed in this Jargon File entry, which is where our usage of "mundane" comes from.