I just stopped by too see the latest from Jon Katz and I find an article about a (weak) facebook hack? Oh....

I made GIS maps for years, always using public data. And there is a lot out there, and it is government subsidized, and it can be of marginal quality. The only nationwide project I am aware of is the TIGER project, which is supposed to release a new, provisional data set every year. When you can get it to work, its pretty good. Federal agencies also often release their own datasets, and we would often have forest service, national park service, and blm data on the same maps, sometimes in overlapping areas. Then there are the county datasets. And the city where I live put out their own dataset a few years back. So there's plenty of data, and it is almost all free. Companies that charge for it often have done post-processing or packaging which I believe they have government contracts to do and are allowed to recoup their investment.

Where trouble often comes in is in projections, spheroids, datums and the like. GIS data on different scale will use a different model of the globe to pinpoint places, will use different coordinate conventions, often related to the agency that produced the set (eg the city always used something called state plane, the fs always uses the nad27 datum, well, mostly). Two datasets that have location information for the same road can be meters off simple because they are not represented in the same projection correctly either by the software or the person doing the projection. And these are just location issues. Tabular data is a whole other thing.

The poster sounds a little uninformed about GIS in general.