I don't know why I feel I have to do this, but I'm now going to mount a defense of the science (or lack thereof) in The Secret and its ilk. Settle in, kids, because I'm about to get all Kantian up in here!
First, some definitions: empiricist, as in "Josh, as a philosopher, is part of the empiricist school because he believes that things in the universe can be known by way of our scientific perceptions of them and that those observations (and only those observations) inform our understanding of the universe around us."
Also: rationalists, as in "others, perhaps Rhonda Burne (or whatever that lady that wrote The Secret's name is) are philosophical rationalists because the believe that things in the universe can be concluded without any external empirical observation. If one were to be born into a vacuum without perception, it would still be possible for that person to rationally draw given conclusions about the nature of the universe based only on the premises they can rationally conclude to be true."
As regards your empirical school of thought, it would be difficult indeed to argue for the science of The Secret. You're right, writing positive ideas on a white board is not, in a scientific sense, going to have quantifiable ramifications. The people who come up with this stuff are not, though, empiricists.
New definition: transcendental idealism, as in "Kant (and maybe Robbie?) was a transcendental idealist because he believes that there are things which we must perceive empirically to know, and that there are things which we can conclude and reason in the absence of perception."
Finally, let's mention what perception means as regards Kantianism: the perceptions of things we have are perceptions of "phenomena," and are only loosely related to the things-in-themselves, which we can call "noumena." The human mind imposes two conditions upon things-in-themselves: space and time. These two qualities are not found in things themselves, but are rather the forms, the preconditions for our understanding.
This has radical metaphysical consequences; imagine your computer, or your desk, or your chair without the properties of time or space. Actually, don't, because you can't. Your mind is totally bound by the ideas of space and time, and it would be impossible to conceive of things without those forms. That's the "transcendental" part of transcendental idealism. Suffice it to say that things in themselves are nothing like the world we perceive.
Back to The Secret- the whiteboard upon which we write our pithy self-help aphorisms is empirically unhelpful. The whiteboard, or at least its existence in time and space, is entirely, though, a function of our own perceptions. In fact, the problems which our little positive blurbs are supposed to fix are also products of our perception, grounded as they are in space and time, with an indeterminate amount of actual relation to those things-in-themselves. So if the whiteboard exercise does something to change our perception of things (which we've already determined is not entirely, but partially, created by the normal functioning of our own minds) then it may have done something to change the nature of the universe as we perceive it. I should be careful to add that our changing perception hasn't changed the universe itself, but it has potentially altered the known world as we perceive it.
This change can't be measured by science, because we have no outside standard by which to measure it. The entire system has shifted, and we don't have a control group by which to compare. Science, or pseudoscience, doesn't figure into this equation. The question here is beyond science.
That being said, I think some of the quantum theory bullshit that they advertise has some merit. Kantian philosophers and physicists, for instance, have written a bit about how Kantian theory has been repeatedly supported by scientific finding after Kant's death. I can see how Schrodinger and Heisenberg, for instance, could be integrated into the argument I've just made pretty easily.
All that being said, I have found "The Secret" and positive thing and self-fulfilling prophesy to be pretty useless. Kant, though, solves every problem.