Twitter came in to the community brought lots of jobs. Did that make the neighborhood better? No. What happened was that the price of housing went up for a group of people who could already not afford it. Basically the "area" was developed but not the "community".
Like an invasive species. There is nothing wrong with rabbits in general. I like them. But in Australia they are destroying the native species.
As humans we have more ability to pick up an move, but we tend to not want to do so. Most of the people in the low end of the economic spectrum rent, so it is not like the increase in property values is making them rich off of their homes, instead they see rent increases.
Trader Joes in the "wrong" neighborhood does the same thing. Many communities "need" a walmart because it will serve their need for cheap food and clothing, and won't raise the property values. It is easy to hate Walmart and other big box stores, but in truth, often a community needs "cheap" more than they need "good".
Edit: Produce is one of the things that are hard to get in a "food desert" Trader Joe's is notorious for having expensive produce with a short life span. http://www.cbsnews.com/news/4-things-not-to-buy-at-trader-jo...