Published: Aug 17, 2012 11:35 AM EDT
Updated: Aug 18, 2012 6:31 AM EDT

NEW YORK (AP) - Facebook's stock has come a penny short of hitting $19 for the first time, meaning it has nearly lost half of its market value since its public offering in May.

It hit $19.01 on Friday, a day after the expiration of a lock-up period that has provided some early investors and insiders with an opportunity to exit.

Investors have been concerned about Facebook's ability to keep increasing revenue and make money from its growing mobile audience, even as many analysts hold positive long-term views.

The stock closed on its first day barely above its initial public offering price of $38. It has been below that level since.

The stock fell to $19.01 before bouncing back to $19.17 in morning trading Friday. That's 70 cents, or 3.5 percent, below Thursday's close.