I got a strand of 50 LED lights from “someone in China.” They were advertised as being WS2801-based, but they didn’t work with Arduino sketches for that chip.
So now I have a 49-light strand, a sacrificial light that I had to rip apart to find the chip identifier (“SM16716”), and an Arduino sketch that proves that they work. Thank you, Google Translate, for help with the Chinese-only datasheet for the 16716.
By the way, there is a probably great library, FastSPI, that supports many chipsets including the 16716. Unfortunately, it just didn’t work for my Uno/strand combination, and I’m not sure why (the code looks right). I’ll probably debug that code and submit a patch.