I would disagree with a broad notion of bad shots: most pictures taken are in fact good pictures, for their intended purpose...
78% of the world population is using a mobile phone (ITU numbers). Not all of them have a camera but photo sharing is now the most used communication media in the world. It 's not because everyone has a camera but because of the existence of an easy, cheap way to share pictures with a group you define yourself, instead of relying on the readership of a newspaper or the contact list of an art gallery. This availability of a cheap and easy to use sharing space for picture in your group has created new uses for pictures. The increase of photos taken is a byproduct of the sharing technology. I mean here Facebook, WhatsApp and the likes, not Flickr.
Most picture are now taken for sharing with a limited group of people, for social connectivity or social cohesion purposes: showing children’s progress to distant relatives, documenting an area of concern, etc … A picture of a child riding a bicycle, a pothole or unlawful littering would not fit the selection criteria of an art gallery, but they are good pictures for their intended purposes and more valuable for the receiver than all “traditionally good” pictures.
Fundamentally, it is the number of photo categories that has changed and the number of different definitions of good or bad. There has never been so many.
There is a positive side for us, proponents of good photos in the traditional sense: photo literacy is expanding exponentially and with it the ability to appreciate photos from other categories. We are now still in the adoption phase of the media/technology. I would guess a further 10 years is needed to reach the “social integration” level where people would intuitively be able to read/appreciate most other photo categories.