This is a speculative posting, so if your BS detector is sensitive, find the next exciting topic.
The Memory Optimizer course contends that we have approximately 11 miles of neural "web" that is part of our inner mind. Our conscious awareness is likened to a 15 inch flashlight beam searching that 11 miles of webbing. The reason we have trouble remembering things is that we haven't effectively created hooks or links to the information in that 11 miles of memory. Without the hooks, we're limited to a much less effective means of searching with our little flashlight.
Accepting this analogy (and it doesn't seem out of line)would seem to illuminate why we have trouble with activation. If PhotoReading a book deposits that book somewhere in that 11 miles, how does the brain determine where to put that information? Isn't it quite possible that it gets stuffed into some remote region with little or no "hooks?" I have this image of the PR'd information being a beautiful hotel in the middle of a jungle. The problem is that there is little or no access. Is it possible that (at least in the beginning) instances of spontaneous activation occur because the book either was placed in a more connection-rich location or it was recognized as being related to things already known so that connections were created quickly? Manual activation, then, is the act of crashing through that jungle to get to the hotel.
Why then, does repeated practice lead to success? Do we become more effective at storing the books? Have we created so many more links that remote regions are less likely?
This would also seem to suggest that regular image streaming might improve activation. If image streaming, through pole bridging, strengthens or creates new neural pathways (just as PRing reportedly does), wouldn't the combination be more effective than either alone? Has anyone used both in tandem and noticed a difference?
Finally, for those who have experienced spontaneous activation, did you find that the topics in which you experienced the spontaneity were often more tightly linked to things you already know than were books for which this did not occur?