Most unions here in LA forbid the use of stringer video that is shot during the daytime. However, it seems to be OK to use stringer video shot over night. Because of that, I find almost all the news stations in LA with a few exceptions do not even have an overnight photographer because they know there are plenty of stringers out there that roam the streets and chase spot news. Many stations feel they are saving money by simply purchasing stringer video footage shot during the night. It is usually pretty easy to spot stringer video as it airs.
Some stringers have an identity or small logo burnt in their camera so that it appears on tape.
Though most stringer video is shakey and sometimes amateur looking, I don't think it is destroying local news. I think there would be a lot of concerns and resentment going on if stations were using a lot of stuff shot in the daytime. The unions feel that would be taking work away from union photogs. I understand that. Sometimes stringer video provides stations who might have missed a big fire or shooting overnight an opportunity to have video for it's newscasts.