Actually, given the meaning if Myth as the use of Story to express a truth recognized by a group that reinforces the members in their participation within that group, I’m not sure that many of those constitute myths.
It is possible that UFOs, for example, play a supporting role in the mythology of some group that either (or both) believes that “the government is not telling us everything” or that “we are not alone.” However, it is difficult to figure out what great truth is expressed by their paranoia or how they recognize themselves as a body. Crystals, pop psychology, and Deepak may touch on various inidividual beliefs (even beliefs held by many people), but they are not expressions of a truth that guides behavior or validates membership among believers.
A modern myth in the U.S. might by the cowboy as the fiercely independent, rugged individualist (a role better suited to the fur trappers, but co-opted in movies and novels by overlaying the ancient knight errant story over that of the cowboy). The cowboy (who, in reality, had more in common with a feudal retainer), has become an image that supports the notions of fierce independence, standing tall against insurmountable odds, a willingness to use violence to support the “right” cause, and a general disdain for authority–all traits that are given some (not universal) approbation in our society. (And where those attributes are not held in high esteem, the word cowboy is often used as an epithet.)
Then what do we call Greek mythology? I’m not sure if requiring a formal organization to recognise something as true is a really helpful definition of “myth.”
At the time that the stories that we have from Greek mythology were created, they were part and parcel of a coherent set of beliefs. By the time they were recorded, Greek society had begun to move away from those beliefs (leaving us with odd tales out of context that do not illuminate the Greek religious belief). They continued to be told after the religion had departed because they were very often good stories (either amusing or profound) in their own rights (and we needed them to give Carl Jung and Mircea Eliade something to write about).
As to a “formal” organization (or even simply any organization), I would not put that boundary on the definition. The group does not need to be orgaized in any way, but the story must provide a means of identification within the group. For Judaism, it is the Sinai experience; for Christianity it is the story of the Birth, Death, and Resurrection of God as man. American society does not have a formal organization for identifying with the myth of the cowboy; it is simply one aspect of the many held beliefs in American society (some quite different, some contradictory) that lead to the overall understanding and self-identity of the American people.
As I noted, I might entertain an argument that UFOs and their assorted baggage constitute myth, although I think there are problems with that proposition. On the other hand, what great story is presented to explain or reinforce crystals? What tale resonates within the breast of a crystal believer? Not all belief is myth. Not all truths are explained in story–and those are not myth.