Come on guys, everybody needs a hobby. HHO is fuel, and renewable. It's just not too practical at the moment, but who knows. It's basically harmless to the rest of us (well, unless you live next door and something goes horribly wrong).
I remember as a kid, the adults were obsessed with metal detectors and treasure hunting. But of course, the equipment was expensive, or a complete rip off, a lot of scams. At the end of the day, mostly it's bottle caps and beer tabs, no matter how much you spent on the detector.
It's just the element of adventure, a chance to strike it rich, with a little luck and hard work. It's just fun to build stuff, to hope and dream. If nothing else, these HHO guys posting here learn a little about electronics, get to see what normal people are building. It will click for some, and they move on to other projects. Electronics is a hobby for me, and have a lot of fun building usual things, many don't work as planned, but usually learn a few things for future projects.