When these things come up on HN I pipe up a bit.

I wrote several implementations of passive device fingerprinting for fraud/security firms and they are implemented across a broad range of industries and companies. I know quite a bit about the shortcomings of these and the challenges faced, in case someone is interested.

Also, just FYI, the big use these days is actually NOT in security or fraud, though most of the companies selling these still say that is the case. The use is in advertising. Most of the companies selling these still call themselves "security" or "fraud" companies, but the revenues from advertising are far outpacing the former categories.