Here in the US there are 2 occasions within the past few months I can recall where something like this happened. Both were military veterans who died and had no known family. It was passed around on social media, and when the funerals actually happened thousands of people showed up.
This is happening here as well. During 2014 Operation Protective Edge, there were several several funerals of fallen soldiers with no known family, in which as a result of a calling from the social networking, ten of thousands of people, crowded in the funeral.