Self appointed in the sense that he piped up at a meeting, or otherwise suggested to the neighborhood association that a neighborhood watch would be a good idea, in light of the recent burglaries and hot breakins. As is not unusual when somebody suggests a task, they are also assigned it. I don't know how many others, if any, schedule time to watch the neighborhood. We do know he's not the only one calling the police. He makes about 10% of the calls from the community.
Yes, that's exactly how things have gone for me with regard to volunteer organizations. I learned a long time ago not to suggest something unless I was ready to do a bunch of the work. :-)
Where did you find that 10% number? Do you have a hard source for it? Even with the "self-appointed" vs. "group" neighborhood watch, the sources I have are only from news stories, and I have found so many news stories that are absolutely wrong, that I am leery about believing anything that isn't sourced properly.