Unfortunately, a portion of the general public is pretty ignorant about the whole photography as a hobby thing. They understand taking family snapshots, but anybody shooting other stuff is "probably up to no good".
Try taking your DSLR into any public space, and particularly somewhere with children in it, and you can see people looking at you suspiciously. The media has whipped up a hysteria about paedophiles and that hasn't been helped by schools etc., (in many places) stopping people photographing school plays / concerts / sports days etc. because of the risk of people photographing kids that are not their own (and potentially misusing those images - in some cases even stating the risk of paedophiles). It is of course pretty ridiculous to US as photographers, but many parents see a DSLR in the vicinity of their little precious and assume the worst.
I have had police called out to "deal with a pervert taking pictures in the park" by parents who were uncomfortable at seeing a camera. This happens at local parks, on the beach etc. I have even had parents come over to me and tell me to "F... off and not bother their children", despite the fact that I was pointing the camera in the opposite direction at the shorebirds feeding on the tideline. Now, I am always very careful not to point it in the direction of children and am there shooting birdlife, squirrels, scenery etc. The police have always been very polite, and apologetic about disturbing me, but they have to check out any reports. I quite understand that and do not blame them at all, it is the parents suffering from media hyped paranoia that are the problem.
Even without the P word, many people just don't like being photographed and, again, are uncomfortable when a guy with a DSLR is taking (to them) random shots. Candid street photographers haven't helped this issue, and their is a TV inspired mental link between big lenses and cops, private investigators and snoopers (particularly worrying to some people for various reasons, if they feel they have something to hide)
As malls etc., are keen to have people find their visits enjoyable, I can understand why they don't want hordes of people with DSLRs wandering around the place making customers feel uncomfortable. Again, the problem is more with the public perception of SLR users than with the mall owners, who are simply trying to keep the shoppers happy.
It's a sad state of affairs, but most of these restrictions are due (at least in part) to many people being uneasy around SLR users. This doesn't get helped by the brigade who do take pictures of the public and stand on their rights to do so, even when they know the person is uncomfortable. I'm not arguing against their viewpoint, just making a comment about the effect it can have.
Heck, even as a photographer, I can feel uncomfortable when I see a camera pointed at me by a stranger, so I can understand it in non photographers.
" and put on the lens cap. No biggie.
