In public places, one should be able to shoot, never had any problems in Romania (or elsewhere in Europe save for UK). But if a shop has a no-photography sign, then it's a condition of entering the shop and you have agreed to it. If for nothing else, to protect the business from out-of-context shots that get re-labelled (intentionally or not).

The kind of damage one can do to a business by twisted photography is very large. I frankly kind of understand them.

I wonder, however, if the people telling you not to shoot don't have the authority to enforce the rule. E.g., if a shop has a no-photography policy, all they can do is ask you to leave, as they don't have the authority to do anything about it and if they break the gear, they pay, no law defends the aggressor. Police can definitely confiscate gear (and detain you).

Either you are in the right and keep it, or you are in the wrong and shouldn't shoot. I hope I'm wrong, but I have trouble picturing (ha) legitimate uses of double-image photography.