The 10 acre thing was a hypothetical example to illustrate a different author's point. If someone else would like to pick up the torch on that one, have at it, but I really don't feel like defending that example anymore, especially when counterarguments range from an ultra-muggy atmosphere to 3 bedroom homes. (Someone could be satisfied with a 3 bedroom home? That's just silly!)
Related to the original question, I think The Secret did a poor job delineating between positive expectation and wishful thinking. I also think WE need to be careful about attributing things to IM when other explanations could work equally as well. Researchers call such conclusions
false positives. (Before you blow off the concept of the false positive as statistical mumbo-jumbo, consider the concept for a moment in the context of... say... an EPT or STD test. That should bring the potential dangers of the false positive home real fast!)
So if you conjured something for yourself, I think you need to be careful about assuming that you did it through IM, and eliminate alternative potential explanations before settling on "I IM'ed it." How do you know you didn't read the mind of a person who had already decided to give the item to you? Or maybe you tapped into the collective unconscious and learned that the item was on its way? How do you know it wasn't serendipity, or a flash of precognitive awareness? Maybe your guardian angel whispered in your ear, and you happened to hear her?
This isn't to be flippant or dismissive... it's simply to highlight that I think The Secret plays into our tendency to want to confirm what we think we know, rather than test what we think we know by trying to disprove it. As a result of the lack of critical analysis, I think the movie suffers.