There's nothing in this video that indicates ultralights are dangerous. Pilot error takes out all kinds of aircraft and their passengers. If that guy had been paying attention and not "flying the engine" he would have been fine. I'd rather be in a well-designed ultralight than a larger single-engine aircraft anyday, if the engine went out.

(and yes, I realize the chances of an engine-out are much, much higher in an ultralight. I can survive after landing a Moyes Dragonfly in a suburban backyard, probably uninjured. I don't think I'd fare as well in a Cessna.)