Photos are nothing but another form of disseminating or capturing information. However, just like any other form of communication, it is subject to falsify reality. Photographs can easily be used to better understand the world around us, yet it can just as easily create a facade over the real truth.
The simplest example of how photos are used to aid our memory is with childhood albums. These albums inform us about a time in our life we might have no recollection of. Without these pictures, people would lose sight of that innocent and carefree time altogether. Sontag claims that "one never understands anything from a photograph", but what about the emotional connection it provides to bridge our daily lives to our past? How do candid photos hide the truth, if they are taken without the subject knowing? For Sontag to make such a direct claim, one could just as easily argue that our words have been corrupted too. Yet that doesn't force us to argue that we learn nothing from speech.
On the other hand, there are a handful of examples in which photos hurt our judgement of society. The biggest example of this that I have faced, along with many online shoppers, is when companies make products look much better than they are in ads and the online photo. After buying the item, you realize that it works nothing like what the company claimed. This is a perfect example of how photos can distort the reality around us. Nowadays, photos can so easily be edited and photo-shopped, that in many cases they do lose their value. Models and actors take photos in "perfect conditions" looking "flawless", but in what way does that illustrate the human imperfection we all carry.
While it is too strong to argue that photos are a "form of mental pollution" because they provide us with a important tool of recollection and storing information, there is a strong current trend which does hurt our opinion of the world. It is important that people understand this, otherwise photos might create the perception that all the world's problems have been resolved.