And lately, it's been a rash of left cranks falling off on Nexts and Roadmasters. "But it's brand new!......."
I have noticed this too when I volunteer at the local bike collective. The cheap three piece cranks that are on a lot of the low end bikes just seem to fall apart. What makes some of them even worse is on a lot of them they don't even have a threaded bottom bracket so you can't just switch to a good used crank and bottom brackett.