Kevin, the reason that soldiers don't like civilian observers hanging around the scene of battles is that they don't always keep under cover. They move with the troops and give away positions as they try to "get the story" be they reporters or Amnesty International observers.
How do they give away positions? They look at you behind that bit of wall. They try to talk to you as you share a bit of cover, distracting you from your job which is keeping you and your buddies alive. That bit of distraction, that look could tip off a sniper that here is a target or that it might be a good time to move since you aren't paying attention.
I could go on but I think you get the picture. I'm not saying that the IDF banned reporters etc. from Nablus and Jenin for this reason, but it would be a damn good reason if they did.

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