[JHL]

When people see movies like "The Secret" and read books about the Law of Attraction, they get the impression that they can reach whatever they want via Intention-Manifestation: you send your intention out to the universe, the universe will arrange itself and manifest the object of your desire.

Some people do this, possibly. But I think you should give credit to others who engage in a somewhat more rigorous enquiry than passive acceptance of what somebody else says is true.

The fact is: I-M doesn't work all the time (that's the least you can say).

This is not a fact at all. Just because its effects arent clear to you doesnt mean the principle has ceased to operate. Its akin to saying that at night the sun stops working.

Now, suppose that it is possible to master I-M and that everybody becomes an I-M expert.
In that case, it would be just a matter of time before all people in the world are happy, rich and healthy, and that there will be no war or injustice anymore.

Everyone already is an IM expert by virtue of the fact that we all have free will and can think. The point is to understand the fact and learn how to direct it more productively.

It's interesting to know that almost all people who defend I-M have a good reason to do this: they promote their own book, their own blog, etc. In summary: they earn money directly or indirectly with this I-M stuff.
Look at the signatures in the replies on this post.

You did say "almost all"

In reading your post (and others) I was reminded of this quote:
"All truth passes through three stages. First, it is ridiculed. Second, it is violently opposed. Third, it is accepted as being self-evident."

We seem to be hovering around 1st base at the moment. I shall gird my loins for the violent opposition that is to follow! And no, that has nothing to do with it being Global Orgasm day today! Come on, people.