Here's something Facebook investors won't "like."
Facebook stock slid to an all-time low of $18.75 Monday morning -- less than half the initial public offering price, following a disastrous performance last week -- and Mark Zuckerberg saw his own personal fortune halved from nearly $20 billion to under $10 billion.
The social network's stock slumped Friday to $19, losing half its market value since the company's initial public offering in May and ending the week down nearly 13 percent.
For Facebook stock quotes and more business news, turn to FoxBusiness.com.
"The market is not convinced of Facebook's future," "The Facebook Effect" author David Kirkpatrick told Bloomberg.
Facebook hit the $19 milestone a day after the expiration of a lock-up period that had previously prevented some early investors and insiders from selling their shares. Stakeholders who owned a combined 271 million Facebook shares before Thursday can now sell their holdings.
Facebook Shares Bounce Off New Low
Plunge in Facebook Shares Has California Seeing Red
'Kenny the Clown' caught with iPad stolen from Steve Jobs' home
Busted! Dell apologizes after found using fake sweepstakes to hawk warranties
Researchers reportedly may have video that shows Amelia Earhart's plane debris
Should Investors Worry About Facebook's Future?
'The market is not convinced of Facebook's future.'
- "The Facebook Effect" author David Kirkpatrick
A breakdown of just how many major Facebook Inc. shareholders sold their stock this week won't be available until next week at the earliest, when sellers must disclose such transactions.
Facebook's stock has struggled since the company's mid-May IPO. It closed its first day of trading barely above its initial offering price of $38. It has been below that level since.
The stock has been down on 38 trading days, up on 25 days and unchanged on one since its initial public offering.
Investors have been concerned about the social network's ability to increase revenue and make money from its growing mobile audience. Many analysts, however, hold positive opinions of the company's long-term prospects.
Meanwhile, stock in tech darling Apple soared, hitting new highs Monday morning of $658, driven up by rumors of an upcoming new version of the popular iPhone.
The Associated Press contributed to this report.