The problem here is that mainstream nutrition "science" is also a fad. It is also a dramatic example on how the Internet + an incentive can produce better Science than the traditional grant (and lobby system). Many of the traditional dogmas of nutrition have recently come intro question: the idea that eating cholesterol is what increases cholesterol in your arteries, the idea that salt is bad for you, the idea that fiber is good for you and many others.
Regarding ketogenic diets, there are so many results and it seems to work so much better than what "they" have been telling us that the idea that this is a "fad" starts to sound a bit silly. Actually, some proponents of ketogenic diets are backing their claims with explanatory models, instead of simple epidemiological studies (which are, in my opinion, the lowest form of Science).
Regarding ketogenic diets, there are so many results and it seems to work so much better than what "they" have been telling us that the idea that this is a "fad" starts to sound a bit silly. Actually, some proponents of ketogenic diets are backing their claims with explanatory models, instead of simple epidemiological studies (which are, in my opinion, the lowest form of Science).
Check out this talk if you want to know more: http://www.youtube.com/watch?v=M6vpFV6Wkl4
edit: this talk provides some convincing arguments against your assumption #1.