or at least it seems to be limited to 2.5, I had reloaded the model in 2.49 and it didn’t have the same effect. As you can see below its give the effect that my wires are too close to each other and have broken through, but they are not. the effect worsens as I zoom out. Is this a feature? and if so how do I turn it off, I find is distracting.
I dont think thats a feature, i took screenshots of same thing, and forgot to report it. (i modeled house)…
So at least you know that you are not only one experiencing this… 
Did you remove doubled vertices? I often get artifacts like this when I forget to remove doubles. Blender 2.5 has uses a different engine and mesh system (as far as I know), so it won’t appear exactly the same. Seems like an odd-looking mesh though, what are you trying to do?
No double verts in that mesh, as far as what it is, it is part of a helmet, aiming for a layered effect so the tight angle is under another piece that I had hidden.
I though it might be the angle was too tight, but I can align to faces parallel to each other and still get the annoying see through effect.
I hope whatever it is fixed or can be fixed soon, it gets very messy with heavy meshes
Definitely a bug. Something with sharp edges and occlude geometry enabled in 2.5. Hope they can fix it
