Love these links! Great topic! Makes me think of that immortal scene (one of several) from Devil Wears Prada, where Meryl Streep scathes Anne Hathaway, telling her why she's wearing teal.
It occurs to me to dust off the definition between fad and trend. Colour of the year is fad in my book, trend is longer lasting...5 to 10 years.
Anyways, I think there IS such a thing as zeitgeist. Some people are aware of it and some are just swept along by it.
I think the sweet spot for an idea must be the vast majority that has certain boundaries and sensitivities, but that can make small adjustments in course (to the point, given time, will find themselves going back in the direction they started from). Trend makers are people who can play it just right and take the long view and never forget the forever core values of most people. It's all very Mad Men. I mean, who ever really needed a slide projector and a smart phone? Except that they are ways to keep doing what we like to do... ie, look at cat pictures
Btw, I feel designers and stores have been very off for quite some time now... I don't know what that says for companies who advise on the matter.