Depending on the specific deals -- Amazon probably gets a better deal than most other vendors -- it shouldn't, as Will pointed out, make that much of a difference in how much money WAC (or whomever) makes on a title. If the label gets, say, 40% of the MSRP, they'll get that no matter what the...
I don't do it often, and haven't in a good while, but I've done it with several movies back in the day. I think the one I saw the most theatrically was Aliens. After seeing it two or three times with various friends in major theaters, it eventually hit a second-run theater in the town I was...