Can tech companies save Detroit?

Sunday's Observer had a good-news story about Detroit. The city, which has been a symbol of urban failure, is now seeing some signs of resurgence, thanks to a modest influx of high-tech start-ups who seem relatively unfazed by the lack of services and facilities.
One of the problems that Detroit faces is that American taxes are levied almost entirely locally, so that with falling numbers of residents and of people in employment, the city is unable to pay for basic services. Hence, in addition to abandoned buildings, there are roads that have not been maintained, and the rising crime levels are made worse by poorly funded police and fire services. But evidently whatever other investment has been missed, there is decent wi-fi.
The situation in Detroit is so bad that there is almost a romantic aura surrounding it - particularly for those who have not been there. Both the main article and a review of Mark Binelli's book The Last Days of Detroit  use the term 'ruin porn' to describe the obsession with beautiful photographs of crumbling buildings. We should be wary of falling into that trap. And a few tech start-ups are hardly going to solve the problems of a massive poor and unemployed citizenry. But it is a fascinating place to study as the solutions that are mooted - whether this latest influx of the bright young or the moves towards urban agriculture - provide a test-bed of what can be achieved by a bottom-up approach when top-down has so manifestly failed.