We should all do some research before we start debating stuff, this goes for me as well. I opened up my iPhoto Library to take a look at it, and here is what I found.
This would appear to be what you are describing, no?
And so on... But MOST IMPORTANTLY, when I change the "date taken" I want the photo moved to that new date!!!!
Unfortunately you are right about this one
Why have this type of file structure? What happens if you loose your iPhoto database?
If you lose your data base, than it really doesn't matter what type of file structure you have, because all your data is gone
Want to stop using iPhoto and use something else?
Then you'd have to import all your photos into the new program. Apple's file structure isn't going to automate this transition for you. Same as if you were moving from a different program to iPhoto...
Apple goes out of business? You are stuck with a MESS of photos that are impossible to find!!!!!!
Apple out of business? Blasphemy!!

If apple goes out of business the programs will not cease to exist. You can keep using iPhoto, or when the time comes to move on, just export all your photos using iPhoto, if using the dated file structure of the finder is too hard.
Tyler
Earendil