While I do not question their qualifications in any way, the article authors did not cite their source of information for the list they provided. The list is simillar but also different from one I used to review when I ran other self-employed endeavors in Minnesota and sometimes had employees. And that's my point. These self-employment test lists vary not only from time to time as government agency policies change (IRS, Workers comp insurance, state tax authorities, etc.) but also from state to state.
That variety, the legal complexities involved, and the continually- changing tax arena underscore the need to have a qalified tax professional in your corner.
With the federal deficit now setting new records, look for the IRS to get more agressive in collection efforts. The changing mood of the IRS, influenced by the changing political winds in Washington, D.C. is one of the things that influences the lists themselves and/or how such lists are interpreted.