Photography used to be extremely expensive, demanding on the participants, and time consuming. It was reserved for only the most special of occasion, including death. Even though photography is cheap and easily accessible these days, the quality of the photo can still be just as meaningful as back in the olden days. Today people may be posting something as useless as pictures of their feet on Facebook; however, people are still taking and sharing baby births, weddings, and other photos of life changing events.
I would say that photographs have evolved from a very serious form of record-creation to a much more casual tool. Photos have been altered and tampered with since the dawn of photography (see the first link below) for various reasons, usually with either a political or a profit motive - that is something that has not changed much.
Culturally, a century ago having one's photo taken was a major undertaking - exposures were long, and the process was expensive and only performed by professionals. As a result, people dressed and posed formally, as they would have for a portrait painter. Only very notable buildings and outdoor scenes were recorded for the same reasons, resulting in a photographic history that does not really give us a feel for the eveyday life of those times. Now, photos are cheap and easy to take and share, so we are recording a much greater sampling of the more routine aspects of our lives.
With the advancement of technology, the photograph has its employment and significance greatly altered. For instance, such a program as Flickr, allows for "a photo and visual sharing community." It has grown into one of the most popular photo sharing platforms of the century.
While the extension of sharing visual images has tremendously been extended, there are other issues involving photography as a means of communication. For one thing, with photoediting programs the old adage of "a picture says a thousand words" assumes a different meaning from earlier days. Whereas a photo would fairly well present a true image, nowadays numerous alterations can be made. For example, a person's photograph can be changed to make him or her slimmer or younger, flaws can be removed from the face, and so on. Journalistic photos also can alter reality as taken from certainly angles a scene can appear to have many more people in it, etc.
When everyone has a digital camera built into their phones, the photo has changed into any mundane thing we can take photos of. With the advent of Facebook, among other media outlets, it's nothing to share photos of your kids doing nothing in particular with their grandparents 1000 miles away. Photos do not mean as much as they once did. I wish this wasn't the case, and photos were treated as works of art; reserved for only special occasions, but alas, with the digital age, goes the sentiment of speciality...