Now, with two of the top five S&P 500 constituents (Google and Facebook) at risk of being regulated down to mere mortal status, it would make sense that the market might consider how these companies would be valued if the liability shield of section 230 were to be taken away (which was the topic of discussion at today's Senate hearing). 

This is contemplated at a time when the techology sector has recently surpassed 1999 levels in sector composition within the S&P 500.  According to the WSJ, tech made up 37% of the S&P 500 market cap in 1999.  It is now 40%.  

As for the Senate hearing today, if you've listened to any of these (today or in the past) it is perfectly clear that these platforms are too big to manage, with unintended consequences that are dangerous to society (if not an existential threat).  We have former computer programmers, turned entrepreneurs, turned information gatekeepers, turned (some of) the most powerful people in the world. 

The leaders of these companies (in most cases, founders) don't know how to tame the monsters they've created.  Zuckerberg, of Facebook, admits it.  Dorsey, of Twitter does not.