Mark Zuckerberg is no longer among the world's 10 richest technology billionaires

SAN FRANCISCO: Facebook shares crumbled again on Thursday, sending the once-feverishly sought-after name below $20 for the first time as investors scrambled to get out of the way of a potential share deluge in coming weeks.

With this slide, co-founder Mark Zuckerberg is no longer among the world's 10 richest technology billionaires. Zuckerberg is now worth $10.2 billion.

Thursday marked a five-day losing streak for the Facebook stock, which has shed almost $50 billion in value since its debut - more than the total valuation of Hewlett-Packard or Starbucks.

The stock debuted at $38 and has headed south since, pummeled by growing doubts about its lofty valuation, growth prospects, high-profile departures.

Now, investors are struggling to understand the impact of the expiry on August 16 of a lockup period on insiders' sales.

That's when the first restrictions barring employees and early investors from selling goes away, opening a spigot to roughly 1.88 billion additional shares for trading by year's end.

Some investors said the stock's downward slide may actually lessen the deadline's impact as insiders opt to wait.