It amazes me that there are still businesses that do not allow people to take pictures while inside. First of all, you are blocking the free flow of information and it offends people. Why would you offend on purpose your customers?
Then, they will use the photo on social media. That is free advertising! Why avoid that? Plus, it’s not a traditional add, so people will pay more attention to a true opinion of a friend.
You try to hide an embarrassing fact? Why? If people see that when they enter your business, wouldn’t it be better to fix that instead of trying to hide it? As a business owner, are you sure that you know everything that happens in your shop? Would you like customers to give you true and free reports about what you need to fix in order to make them happy? No more mystery client!
In fact, what you should do is to encourage people to tweet about you, to post photos with what they see when they buy from you. Engage them. Thank them. Not like the security guy at one supermarket who called the police because I took a photo and posted it online and he was upset about it.