This graph shows the tweets for several hours over a Sunday afternoon in Chicago. Though the graph clearly shows tweets coming from most areas in Chicago you can see a clustering in the down town area and the near north, along with a large cluster in the near west suburbs and north shore. These area are popular with wealthier more educated communities in Chicago, and their higher level of tweeting shows their continued higher access to new mobile technology, ability to pay digital roaming charges, and ability to exploit innovation.
But just because the map shows more tweeting in certain areas the story is not entirely negative for poorer communities in the south and west. You are still seeing more tweeting coming from these poorer and more ethnic communities than you generally see in most suburbs. So despite inequality of access there is still growing access to new media among many in the traditionally more disadvantaged communities.