When a former high ranking official preaches for a particular solution to a problem - maybe that former official might know some things about the cause of the problem, and know something about the best solution. Clearly the former official as a former insider would have better insight to the problem than us typical normal people. Or maybe, just maybe, that former official is abusing an emergency to push a product that he's being paid to promote regardless of how good (or not) that thing is.
When Michael Chertoff, the former DHS secretary, is repeatedly calling for installation of full-body scanners for airports. Well, maybe he knows something or other about the matter. But what if he and his lobbying agency were being paid by the manufacturer of the machines in question?
Regardless of how good (or not) those machines are - that Chertoff is being paid by the manufacturer makes this smell.