Statistics found at http://www.census.gov/prod/2008pubs/p60-235.pdf
1. I think many people would be interested in this information: Politicians, hospitals, community health clinics, and insurance companies to name a few.
2. The data was collected by the US govt using the current population survey (CPS). The data collected asks questions related to the previous year's coverage. The survey takes place between February to April as part of an income survey. The data reflects annual data collection from 1987.
3. The most recent numbers are from 2007, and show a decrease in the percentage of uninsured Americans from the previous year: 15.8(2006) to 15.3 (2007). It also shows the reported number of uninsured Americans to be decreasing over the same time period: 47M(2006) to 45.7M(2007). In a related stat, the survey showed that the number of people with health insurance actually increased from 2006 to 2007, and the number of people insured privately fell over the same time period.