Wait, you can't really "make" someone hold onto their stock, can you? Like have a condition for continued employment be don't sell?
I'm guessing it will just be market forces: a bunch of twenty- and thirty-somethings with credit card debt or an eye on Tesla deciding weather to cash in those pieces of paper.
You assume those people have stock. That is very unlikely to be true. Most of those people have stock options. Very different.
An option means that I can buy a share of stock at some guaranteed price (strike price). So, I would actually have to cough up the money to buy the share. Only after that, do I now own a share of stock that I can transact as such.
If the strike price is above what the stock currently sells for, I probably do not want to exercise the option. If the strike price is close to the option price, I probably would rather hang on to the option until the price rises some more. The option doesn't cost anything until I exercise it (or lose it, most options have a time limit) so I mitigate risk by waiting.
So, unless the stock price is above the option strike price+some margin, people won't transact.
My uncharitable speculation was: What better way to keep everybody from flooding the market with Twitter shares than to drive the price down enough to keep people from wanting to cash out their current options.
To be fair, the depression in Twitter is probably just everybody getting a shock that "Gee, Internet companies can actually saturate a market and run out of growth."
Amazon got zapped recently (imagine, adding sales tax to their prices dropped their sales). Google and Apple are showing some signs of deceleration (ad revenue is slipping because smartphones have saturated all markets with real money--so now everybody is actually chasing a competitor's customer rather than bringing in new users).
I'm guessing it will just be market forces: a bunch of twenty- and thirty-somethings with credit card debt or an eye on Tesla deciding weather to cash in those pieces of paper.