It's not just posting photos that can cause this kind of trouble. I get a lot of email intended for other Doug Webbs sent to my gmail account, with variations on the presence/location of periods, or CC'd with another gmail account that's the same but with numbers on the end. For a while I was getting boarding passes from a major airline for a Doug that was frequently flying up and down the US west coast. Those emails…
This is most likely intentional.
Most business travel gets booked by assistants / travel agencies / client reps / etc. They are going to use their own account when booking tickets, and then forward reservations or boarding passes to the actual passenger. That passenger then wants to for example reschedule in a hurry when a meeting overruns, or change seats or meal choice without having to explain their seating preferences over the phone (is 25C still available? No? Then get 27A).
Security wise it would be better to have some sort of delegated permissions system, where the travel agent can add email addresses who are allowed to access the booking, you then have to create an account with the airline and prove that you own that email... but I don't see the airlines pissing off their most profitable customer segment with extra hassle to add protection against misforwarded emails.