This is a problem, a bug, ...a feature?? Well, many of us have it, ALL of us should write to the iTunes feedback.
http://www.apple.com/feedback/itunesapp.html
Couldn't find a specific "App Store" page for that, but hey it worths a try.
I have trashed a huge app countless times, and iTunes insists in downloading it again everytime it checks for new downloads. I don't want this app anymore, I want to get rid of it once and for all, why can't I?
In spite of this bug, hope you all have a happy new year.
JJ