Looking at the sifferkoll web logs for April, and making the assumption that most people with an LENR interest at least visited this site once, my estimation is that the “hard core” followers consists of roughly 15,000 individuals (IP numbers).
I’ve also checked IP’s for all the downloads of the Lugano Report from sifferkoll. Before I’ve stated that summarizing the per month unique downloads point to some 200,000+ IP numbers, but it seems like most people downloaded it about twice, so the real unique number is ~110,000 downloads from sifferkoll. The Lugano Report though can be downloaded from a number of different sites; energiforsk/elforsk.se and University of Bologna, being the more official once. But external links usually points to sifferkoll.
Interesting to note is that the article with the larges external direct reach was this one on extremetech.com
All together though the report might have been read by 150-200,000 individuals, and maybe LENR as a concept/possibilty is known by 1-2M people around the world depending on how much talking is going on.
The core of arguing on the forums is very small though. My estimate is that less than 1000 individuals is actively participating with the volume of work produced by less than 100 individuals. The lurking is huge though.
And it is spread through out the world with a focus on the US in absolute numbers, but on a per capita basis centered in northern and eastern Europe. Here is a picture showing a sample of the Lugano Report downloads on per capita basis.
And, this is what it looks like right now following the latest ~500 visitors on this site continously (updated every 5 minutes or so).