Maps like these make for really interesting conversation, and some really cool looking graphics, but that's about it. To say that people naturally gravitate to their own kind, in similar social/ethnic/religious groups....well, we all learned that in 5th grade world history. It's nothing new and I don't honestly believe it will ever be any different. People naturally seek surroundings where they will feel most comfortable and accepted. I don't think any of these "divides" were engineered (unless you count I-10 and the MLK Expressway). I think this is simply the natural course of human behavior.