Interesting findings. The melatonin and cancer link has been studied for quite some time. Nocturnal lighting reduces overall melatonin levels in all mammals studied. This study compares ambient nocturnal lighting (urban lighting as measured by satellite imagery) and breast cancer incidence and finds a correlation between the two, but not between nocturnal lighting and the "control" lung cancer.

Funniest anthropomorphism in the article:
Scientists have known for years that rats raised in cages where lights are left on for much of the night have higher cancer rates than those allowed to sleep in darkness.
Rats are nocturnal. They don't sleep in darkness.

Most predictable blog reaction to the final quotes in the article [why CFLs were even mentioned is beyond me]:
Will this finding spark a battle between the toxin and global warming wings of environmentalism, or will they compromise and demand that we all just sit in the dark?
Heh. I'm guessing most of us could avoid catastrophe by simply switching off lights, computers and TVs and installing heavy shades where we sleep.