This list is misleading. over half are from the Ann Arbor area and a few are in California (and other states) with a few remote offices in Ann Arbor. They really should be pushing for Ann Arbor to be a tech center, not Detroit.
The Detroit "region" or sometimes known as "Detroit Urban Area" or "Metro Detroit", is actually quite large and has many beautiful communities with in it. This wikipedia page sums it up well. The "region" is actually the 9th most populated urban area in the US.
http://en.wikipedia.org/wiki/Metro_Detroit
People also forget how large the actual city of Detroit is. If you look at the map linked below, you'll see that Boston, San Fran, and Manhattan all can fit within the city limits of Detroit.