In a comment added to the Hacker News message, Facebook securityengineer Matt Jones said the links were typically only sent to the email addresses of account holders.
PUFs are an innovative way of safeguarding individual chips from data theft by using the unique 'fingerprint' inherent in every semiconductor device to protect its encryption key, making it very hard to clone and thus reverse-engineer and compromise security microcontrollers.
He also worries about the security of his own job as a civil engineer at Bechtel, where he says layoffs are imminent and jobs have been moved to New Delhi.