Honestly. The correct way is to take pics with your cell. Then ask to use the bathroom (even though you're not buying anything) and comparison shop in privacy.
Best Buy once told me that I was prohibited from taking pictures in their store. They said it was for loss prevention.
After I got over the shock, I handed everything in my hands (small stuff) to the manager and then went to Office Depot and bought my new Color Laser Printer there instead. They lost at least $600 in sales that day over that policy.
Why was I taking pictures? I saw a game that I thought my friend in Norway would like, and I was going to tell him about it.
The only thing I can imagine is if they're selling stuff with visible online registration codes. And I thought everyone stopped doing that years ago.
At any rate, it's either just a few Best Buys or they've never caught me doing it, or the employees just don't care, but I've taken pictures in Best Buy lots of times. Mostly to share laughs about their ridiculous HDMI cable prices (and other AV products) in the Magnolia AV area.