the typical use for a feature like this is borderline illegal (taking photos against someone's will)
Taking photos against someone's will is not unethical, and in most democratic countries that respect freedom of speech and freedom of the press isn't illegal either, like in the United States. In some countries, publishing a photo might be illegal in certain circumstances, but just taking a photo and refusing to delete it normally isn't. There are many cases where a fake delete functionality can help a photographer or photojournalist to escape illegal oppresion and serve the public interest and society at whole. Many photographers and photojournalists regularly use hidden cameras and spy accessories (e.g. mirrors in front of a camera lens to take photos behind the photographer's back, etc.). Three years ago I took some photos of policemen beating a black woman violently but they saw me and they beat me with their globs as well and forced me delete the photos while watching me playing on the LCD all the photos I had taken and hitting the erase button not only for the photos they were in but for ALL the photos that showed other police officers too from that day. I'm sure they didn't want to leave their fingerprints on my camera, otherwise they'd have taken it from me and destroyed it. Problem is, I'd undelete the photos back home but I couldn't because I had to take other important photos later that day from the same political demonstration (again, some of them involved police brutality that I was thankfully able to publish them). From that day I always have a wearable camera on my hip recording everything in front of me the whole day, every day.
Most countries are members of the Berne Convention which created the international copyright system. A photo is copyrighted the time it is created even if its creation violates the law and becomes the property of the photographer, thus nobody can demand the deletion of a copyrighted photo except a court of law with the approval of a judge.
In the United States no person has the right to refuse to be photographed, but there are laws (e.g. defamation and privacy laws) which control how a photo can be used and this rarely involves the will of the photo's subject. If it were otherwise and the subjects of the photos had to agree to be photographed, then freedom of speech would be curtailed and very few people (only those who wanted to promote themselves on the press) would agree to be photographed and society would lose its visual history. There are serious reasons why spy cameras and no-privacy-in-public-spaces laws exist.
Other that photojournalist involving police brutality, there are also simpler cases where taking a photo against someone's will is socially beneficial and ethical. Some people don't want to be photographed because they are criminals or their actions damage society in some way. Some people simply have the irrational belief that a photo steals their soul. Some other people just dislike the idea that a photographer can make money with a photo they appear in. I was doing social documentary photography one day and I took a photo of a large mass of people with a wideangle lens when one person started yelling and demanded I delete the photos simply because she was barely visible (like everyone else) in a photo of more than 500 people who had gathered in public, with other photographers and television crews there as well. Another time I took a photo of a political candidate who harassed me strongly attempting to make me delete the photo. As a photojournalist and photographer the first thing I understood in my career was that the consent of the photo's subjects should not be what dictates whether a photo should be taken, published, or viewed as moral or immoral. It's all about the use of the photo and the purpose of the photographer or publisher that determines whether a photo is OK to be taken or published.
