[M] (4) CD Quarantine Zone

• Very large amount of space, to allow for easier building placement for Terran/Protoss (Terran especially)
  
• Fair distance to the ramp; with Zerg players having it easier than ever these days to start spreading their creep, forcing a bit of extra effort spreading it between the main/natural helps to scale that back a bit in the early stages of the game, lest they be subject to early drop/air harassment.
  
• Mineral lines relatively safe in the corners of the map; no possible cliff/ridge exploitation to deny mining.
  
• Most of the cliff is not exploitable due to terrain features

Basically, I wanted to be the anti-Entombed Valley on this one in terms of size of the main. This also opens up the opportunity for me to experiment with the recent 5-range queen patch; up until now, maps have been mostly balanced with the idea that Zerg won't be advancing their creep very far in the early stages of the game (simply because it will get denied). With that increasingly no longer the case, the map itself is adjusted to help keep early game creep spread in check. It's not major, but starting your first 1 or 2 creep tumours in the main will slow down the outward spread for a short while, and the punishment for not doing so is greatly increased due to the distance between hatcheries.

• 3 barracks/gateway/evo chamber-wide choke at the natural, allowing for reasonable FE opportunities for all races. This is offset by the vast size of the main, which can be subject to drop/air harass.
  
• Not much else to say, pretty safe and standard natural

The natural works heavily in conjunction with the main; where the natural is very small and secure, the main is very large and prone to air-based assault. An offensive player looking to push into the natural would first need to force at least a portion of the defender's troops back into the main to hold off any attack there, then push into the natural choke while the defences are thinned out. For the defender, it also becomes reasonable to take the natural without having to worry about an overwhelming force simply breaking through (unless, of course, you simply defend the choke poorly). The design forces more strategic, multi-pronged aggression.

• Wide ramp on the defender's side to prevent an aggressive player from indefinitely holding that position and denying the third
  
• Small ramp toward the centre of the map, making it very easy to defend the location with a small set of key defences
  
• Sits beside a ridge, allowing for air and drop pressure against an opponent who is too greedy and sparse in their defence, due to the small ramp
  
• Fair distance away from main/natural by ground, removing the "freebie" aspect of 3-base economy; this is offset by the easy to defend ramp
  
• Given similar distances, the adjacent corner's third can be taken in the event your usual third is located beside the opponent's natural; this is optional

The basic idea I'm going with here is a third base that is viable to take, given a player with decent positioning and map awareness, but is by no means handed to them on a silver platter. The distance between the natural and the third also means that your main base is not automatically defended by taking the third. My theory is that players will be less inclined to death-ball their army, and if they do, then there will be many opportunities for an opponent to pick them apart. The map layout also allows you to take an alternative third base (e.g. middle left if you spawn top left), forcing the opponent to either go through you, or take the long way around and put his army way out of position.

All the above points apply, but you might notice there's no dedicated 4th base; you'd be going into a different corner and taking its main, natural, or third. In other words, your bases are getting more spread out, but in a way that isn't as bad as what we've seen in the past. For example, taking a 4th on Tal'Darim SUCKS. Why? Because if your opponent sends his whole army to kill it, there's no real opportunity for you to punish them for going so far out of position. You can't really trade a 4th for a 3rd, for example, because he'll just keep going into your own 3rd before you can do anything about it, you'll move into his natural in the same fashion, etc. and you have a base trade. Looking at this map, let's assume the following scenario:

You spawn top left. Your opponent spawns top right. Your 4th is the bottom left natural. If he sends his whole army to go kill your 4th, and you're somewhere like in the centre of the map, you can go kill his third and you both have the same-ish walking distance to your natural -- and let's not forget that your reinforcements will already be there to defend anyway. Heck, you could even go run toward his natural choke, split your army in two, send half into the natural and the other half into the third. While his army is on the other side of the map unable to do anything about it, you lose your 4th for his natural and 3rd.

That's theorycraft of course, but the idea is that more spread out, fewer overall bases discourages deathball play. That's how things worked in Brood War; there's no reason it shouldn't work the same in SC2, even given the different units and mechanics. The best way for these kinds of far away bases to be shut down is through harassment, which means supply and resources split away from the main army. It makes for more dynamic, multitask-oriented play -- i.e. more skill is required.