It's pretty shocking how many commenters are blaming the individual for not "trying harder" to find contact information. It's pretty clear a16z didn't want to pay anything or appreciate the disclosure at all.

Finding random email addresses and sending them a notice would have gone no where other than spam folders. I get dozens of "disclosures" every week from mostly script kiddies that think my DKIM setting is somehow going to be the end of my business. My brain automatically ignores emails like it.