And thats what I mean. While the AP line has been around the ability for everyone to post pictures and "report" news has increased. Lets just look back 50 years. 50 years ago, a patron at the park gets hurt, emergency vehicles are called for, maybe the local AP reporter gets wind and is able to get to the park moments (maybe within the hour, maybe the next day?) later. Takes some quotes, writes a blurb publishes it to the AP line and its sent out to all subscribers of the AP, who then run it in the afternoon or morning papers.
Versus today, wheel falls off of the cart. 5 or more people get their phones out, take pictures, maybe one has a video made. Pictures and video are posted to twitter, facebook, etc. Local people start talking about the story online. Local news organizations get a hold of these pictures, call for witness statements, call the park. Reporter may be able to do the whole store without actually stepping foot in the park...
Plus as you have stated before the need to fill 24 hours of news also helps the minor stories become big. Even 15 years ago, this event may have been mentioned once on NBC nightly news or similar. Now it gets at least 30 minutes on a 24 hour station. If that 30 mins gets a ton of views comments, then it will be brought back up more and more...