StarCraft 2 Custom Maps conclusion: Perhaps the capabilities of editing are so extreme that they are indeed considered... Mods.
All right, I have to get in on this.
Maps and mods are separate concepts. Blizzard is trying to equivocate the two, but doing so destroys the meaning of these two words. DOTA for Warcraft III is a map, but Blizzard wants to call it a mod based on the extent of its gameplay changes. If I were to make a map in Warcraft III that increases the health of a Human Footman, thereby changing gameplay, is that now a "mod"? After all, I've done more than just terrain! What if I altered the health of two units, three, ten, or even all units? How much do I have to change, and to what extent, before we can call my map a mod by Blizzard's definition? What if instead of altering any gameplay, my map just has a new 3D model for the Human Footman? What if I change the lore by calling them Men of Gondor?
In Starcraft 1's campaign, you have what are called "Commando missions" where you navigate the inside of a building complex with either a single unit or a small squad. There is no base building, resource mining, or any other fundamentals of Starcraft's RTS gameplay beyond unit micro. Is this map now a mod, because it changes standard gameplay? How about the missions where you control units with enhanced health (heroes or ultra-units, like Hunter-Killer Hydralisks)? Or how about missions where there's a new, unique building graphic (Xel'Naga Temple)?
Where do you draw this subjective line between a map and a mod? Or are the terms to be synonyms?
The game Oblivion, by Bethesda, has a mod that adds thousands of beautifully detailed book covers to the many books that abound in the game. It does not affect gameplay or lore, but changes the textures of a tiny aspect of the game that is there only for flavor and immersion. Despite this limited effect, it can
only be called a mod. Why?
Mechanically, a mod is a (typically temporary)
modification to the game engine or core data files, replacing/adding content/code.
Wikipedia Article
Mods can replace or add new content to the underlying game (such as with the Oblivion example), they can create an entirely new game atop the original game's engine (like with Counter-Strike on Half-Life 1), or they can even apply bug fixes as an unofficial patch. These changes exist, structurally, above the map layer, therefore affecting all maps (or a subset of maps, depending on intent, such as with entirely new games like Counter-Strike).
Can DOTA be a mod? Yes, but so long as it only exists on the map layer, no matter how powerful the map editor becomes, it is still a map. It is not the
extent of data or asset change that qualifies something as a mod, as Blizzard would have you believe (look at the Oblivion example), it is its place in the engine's structural hierarchy.
TL;DR.
