My original MBP could not be ,aid back in bed with at too much of an angle otherwise the display would flop to an almost closed position. When I took it into an Apple store, they told me that all 17" MBP's did this because the screen is so large and top heavy; that it was a design flaw.
That said, I recently sent my 17" MBP into Apple for a replacement MLB. While it was there I had requested that they try to tighten the display hinge so that it wouldn't flop closed on me anymore. During the interim I would call Apple every day and inquire about the progress. Then mentioned that among the parts that were ordered to fix my MBP, one part# indicated a display housing. When I got the MBP back last week, I no longer had the problem of the display shutting. yes if I hold the machine at a complete 90 degree angle it will most certainly close, but casual laying back no longer does it.
In the end, I think all stock units are torqued to a factory set standard and that is why it was reported as "normal." If you complain, they will do something about it.