Additionally, the city makes many caveats, like "The data is not the product of a scientific survey. All data was self-reported. Individuals were able to submit anonymous reports. Individuals were able to submit multiple reports concerning the same location(s). The City of New York has not independently verified the existence of actual service problems at the reported locations.

You can see the Density of Reported Mobile Phone Problems, and naturally, the most problems seem to be in the areas that are densely populated - both residentially and commercially. The other part is the Mobile Phone Problem Report, which looks at problem areas carrier by carrier. Overall, most carriers seem to have many problems areas, except for Cingular (report here), which might be a result of less market penetration leading to less reporting of their problems. And, of course, people who have problem with service are more likely to report them than those who are content wtih service. Other carriers surveyed: ATT (report), Nextel (report), Sprint PCS (report), T-Mobile (report), and Verizon (report),