There is definitely something wrong with your unit. I have a 13" ultimate so YMMV but my hinge is very tight. In fact, when lifting the lid, I have to press down the keyboard or the entire macbook will just lift up together with the lid.
When I lift up the screen from the closed position I do not Have to hold the body down to prevent it from coming up.
I have had any macbooks and have to say this is the most loose of all of them.
I was at the apple store today and the 4 11.6" airs on display where loose like mine. The 13" airs where tight. I'm thinking this is just how the 11.6" model is.
I thought they were trying to make the hinge not too tight so that you could open it without having to hold down the keyboard. Its a balancing act. Given how lightweight the 11" is, you can't make the hinge tight because you'd have to use two hands to open it holding the keyboard down.
The first 11" I had was pretty loose, but seemed fine. I ended up returning because I was undecided on the 11", but ended up eventually getting a second one which it tighter.
Neither seemed defective.
OCD crazies
Nobody's getting the shaft. The hinges on the 11'' are looser than on the 13" and this was noted in every published review of both notebooks. This includes the wobbly lid when lifting.
The hinges on the 13" are, I think, a tad wider and therefore can take a little more stress. Tighten those on the 11" too much and something will snap.
Price you pay for being thin and anorexic. I believe the standard answer on this forum is that the Macbook Air needs to be less of a girl and go and lift weights or something.