The only places where I have been told that you cannot take pictures are backstage areas that you get to see when taking a tour. The only other places are normally inside shows and some rides (where flash photography and externally lighted videos are prohibited). In terms of outdoor locations that you might walk by, I've not heard of any limitations/restrictions.
The only other place/time I can think that they might ask you not to take a photo or at least to avoid being intrusive is at someone's wedding.