Essentially, free market relies on certain assumptions under which the supply/demand 'invisible hand' works properly and the benefits of free market are realized - the key economics 101 assumptions are (1) large amount of both suppliers and buyers; (2) small barriers of entry and exit; and (3) full and truthful information about market conditions. The further we get from these assumptions, the less free (and usually worse for the people) the market becomes, and often we need gov't intervention to ensure that these assumptions stay true and the market behavior stays close to theoretical free market instead of degenerating into an exploitative uncompetitive monopolistic market with hidden information - as the USA medical market is doing, and seems to need such intervention.