Sort-of memes that are cracking you up at the moment

We can probably look at Ratner jewellery sales to find out.

It's probably more a power curve... if you happen to have the social media incidents which are at the top of the curve then craters your business, but for every other incident (the vast majority) there is no impact.

So really it's just risk management... most of the time you get away with it unscathed, and once in a million times it makes the brand extinct.

This one wasn't an extinction event, but others will be.

Yep, Advertising and PR for a brand like Burger king (impulse purchase, oligopoly, high brand awareness) will only be driving a very small proportion of their sales.
I worked on a large pizza chain who spent a lot on media and it drove about 5%, but then that 5% is millions of £ in sales, so that is still a significant amount of money.