It's funny, I'd forgotten about this until last night - I made a Bargello a couple years ago when I was a newish quilter and I took a TON of photos of fabric while at a local shop and nobody said anything or gave me weird looks (that I noticed). I was stacking up bolts and shooting them in black & white to check values. So either they could tell what I was doing and knew I wasn't trying anything "funny" or they just didn't care at all. And that's good - if I'd been hassled about it I wouldn't have spent nearly $150 on fabrics there that day or become the regular customer that I am now! NOW they all know me, LOL, but at that point I was a stranger.
I know small shops in particular are wary of thieves, so I make sure to always meet the staff's eyes and say a friendly hello when I walk in. I think that goes a long way to putting people at ease if you appear open and friendly. It's not really my job to make them comfortable with me, but it doesn't cost me anything to be friendly. And I expect the same in return....and if I don't get it, I don't usually feel the urge to go back.