Public funding of science, and access to information

On multiple blogs over the last few months, I've read comments from lay-persons (that is, nonscientists) that say, in essence, "As a citizen, I paid for this research, and therefore I should have access to all the data and all the software necessary to analyze that data."  The implications are (1) research funded by the public should be publicly accessible; and (2) the researchers themselves sometimes/often? hold back information or misinterpret the results, perhaps because they are biased and have an agenda to further.  

Now, as a pragmatist, there are a number of issues here.  For example, making available raw columns of tab-delimited numerical data and, e.g., matlab code, won't give a nonscientist the technical know-how to do analysis properly, or to know what models to apply, etc.  Things really get tricky if the "data" consists of physical samples (e.g., soil, or ice cores, or zebrafish)....  Yes, scientists that are publicly funded have the responsibility to make their research results available to the public, and to explain those results and their analysis.  As a practical matter, scientists are not obligated to make any interested citizen into an expert on their research.

While this is an interesting topic, I'd rather discuss a related issue:  How much public funding triggers the need to make something publicly available?  For example, suppose I used NSF funding to buy a coaxial cable for $5 as part of project A.  Then, later on, I use that coax in project B, which is funded at the $100K level by a non-public source.  I don't think any reasonable person would then argue that all of project B's results should become public domain because of 0.005% public support.  When does the obligation kick in?  Just an idle thought on a Saturday morning.