"Its market value surged from about $US55 million to over $US6 billion [...]" Pretty bonkers: https://www.abc.net.au/news/2021-01-16/signal-telegram-faceb...

Really undercuts the argument for the efficient market, at least in the short term!

I feel the entire history of capitalism undercuts that argument!

What's even more wild is that the executives/directors didn't sell any of their stock on the massive increase.

Quite likely they aren't allowed to sell whenever they want, they may be subject to an open trading window, or a fixed sell-down plan over the year.