Since it's the result day after public UK vote, it's worth reminding the last major result day ("Brexit" referendum) was day Kogan signed Facebook's agreement and NDA about Facebook data he had taken and sold to Cambridge Analytica (used a few months later in '16 US election). 
Facebook called it a "coincidence" as to the timing despite that being the day when the risk of any public disclosure dramatically increased for Facebook. It was only weeks after Facebook had to significantly change "Trending" due to political concerns and pressures.
and just because you can't make this up, a reminder Kogan's co-signatory, Joseph Chanceller, and partner on the deal to sell the data to Cambridge Analytica had been hired and put under a Facebook NDA seven months earlier (Nov 9, 2015).
and yes as far as we know, Zuckerberg, Sandberg, Schrage weren't deposed or asked questions about any of this at hearings or with SEC or FTC investigations despite this fairly clear covering up of facts which cratered $40B in stock value less than two years later.
