Ok, well since the last time I read anything about building 7 I have forgotten most again. I also didnt read those links just above.
However, and now I'm not saying that this is conclusive, but I will only propose a few things.
Firstly, engineering is a lot more complicated in buildings than many people probably make it out or think it to be. Now there have been buildings that have collapsed, merely because they were built, and maybe built slightly wrong or with some slight errors in load calculations. Let alone now, here we had a building that had many possible unforseeable things affect it.
Now although no plane hit building 7 directly, think of the other things that may have affected the general structure and integrity of that entire building. First of all, a fire. Yeah, that alone shouldnt be enough. What about the fact though that two really large buildings fell really close to it? ( I don't know what the layout was there, but I would imagine they were rather near to one another.) The pressure alone, might have been able to do some minor damage, and assuming that some of one of the two towers took out a major support or two, well, then things are already looking worse. Ok, again, since I don't really know what the foundations or anything looked like of the entire area, this is again just an assumption. So if the foundations were at all somewhat connected, I'm sure that the fact that all that weight fell onto the one, then it may have somehow affected the foundation of Building 7.
Now, especially after my rather weak explanation, I wouldn't expect you to just say, "sure that makes sense." I for sure don't think what I just said proves that it fell on its own. All I'm saying is that it sure wouldnt suprise me if it did. It's not like it didnt have no reason to.
Engineers build on safety factors. Safety factors are generally calculated on known events; condition; effects. I doubt the fully took into account of what would happen if the two towers came down around it. Even if they did, it's not something that they could ever fully calculate correctly. The thing about Safety Factors is that they are assigned in a certain way so that the engineers think they have covered every angle and made the structure that much stronger than it needs to actually be to cover for something that may happen. However, if you don't ever fully know what is going to happen, you can only give it so and so high a factor. Thus, saftey factors themselves are really only an educated and fairly calculated guess of what can happen. However, it sometimes happen that they arent high enough, and it will happen again.
(This next thing isnt in response to you)
As for the two towers themselves, I have no doubt in my mind that they came down due to the planes. It is really quite incredulous that people think otherwise. All one has to do is simply watch a video of the tower and take note of where it first fails. It is beyond me how that isn't clear enough for some people. To say that explosives were planted, would then have to mean that the Government would have had to plan exactly where the planes would hit the buildings. Give or take a floor or two. I mean, simply watch the building to see where it fails... At the bottom...? No.