[deathanatos]

The news of the SEC investigation seems to be the cause behind the stock's recent drop from $307/share to $270/share, though; if I'm doing the math right, that 12% translates to ~$6.3B worth of value. Kylie Jenner's tweet "only" erased $1.3B of stock value. So, I think Elon has her beat.

That still doesn't seem to be enough to be the most expensive tweet, though. That honor seems to be this tweet[1], where a finance firm "Selerity" tweeted Twitter's missed earnings report prior to Twitter really announcing it, costing Twitter ~25% or $8B. (The earnings report was uploaded early to the investor relation's page on Nasdaq, apparently, and it showed that Twitter missed its earnings.)

[1]: https://www.bbc.com/news/technology-32511932

[sokoloff]

Selerity tweeted content that was already posted on Twitter's IR site. That $8B was likely to evaporate the following day anyway. (Weather forecasters who predict a hurricane don't cause the billions in hurricane losses either.)

Social media gaffes of the "optional" variety (Kylie, Elon, Roseanne) are a different category IMO.