I feel most of the writeups above (mainly Purvis, QXZ) use a rather loose and somewhat confusing meaning of the word fascist, although ryano has put it in its proper frame. Taken the term strictly, fascism means the ideology that allows the state to opress its people, and to believe that violent forcing one's opinion onto consenting adults is justified. In essence, fascism is the ideology of supressing the individual for whatever cause the state chooses to pursue (economical, political, social, war against other states etc.). A libertarian or a neo-liberal, laissez-faire advocate, anarcho-capitalist is the exact opposite: he believes that the state should have minimal (or none at all) interference with the individual's economical and social life. What it undeniably guarantees is the individual's freedom (whether it also guarantees its well-being is another issue, and is heavily debated).
Analogies may be helpful sometimes, but they can also be totally misleading. Saying that neo-liberals are analogous to fascists because they both "absolutely base their faith on something (market/power accordingly)" is a rather unfortunate (and trivial) comparison that proves no deeper connection between the two terms.
So if we want to define the term "market fascist" (a term which is probably self-contradicting) literally, we might say that it characterizes a person that uses state power and legislation in order to benefit large corporations and monopolies, a system that any sincere neo-liberal or libertarian would loathe.
In the sense that the writeups from Purvis and QXZ define "market fascist", the word fascist can be seen only as an exaggeration or irony, in the same way that we can label a doctor a "life fascist" (he bases his faith on the value of life).