Little more than a month aftershares of  Facebook (Nasdaq: FB) hit a new low on the stock market, the company is back below 50 percent of its IPO price of $38 a share.

Despite a brief resurgence after Mark Zuckerberg publicly admitted his missteps and promised to renew the social media giant’s focus on transitioning effectively to an increasingly mobile marketplace, shares fell just below the 50 percent mark on Thursday, closing at $18.98.

While Facebook and close partner Zynga’s (Nasdaq: ZNGA) continued struggles in the stock market have cast a pall over Wall Street’s general confidence in Silicon Valley’s social media craze, the ubiquitous social network managed to reassure investors earlier this month when it finally reached the 1 billion member milestone. But a report last week from the influential analyst firm Sterne Agee questioned many of the new features Facebook has been aggressively promoting in an effort to convince its critics that its core business can support continued growth of more than its user base alone.

Thursday’s stock tumble, however, came after a new study from Facebook app developer Napkin Labs reported that only 6 percent of fans on Facebook actually engage with the brands they “like” there.

More troubling than that number itself, however, is the weak form most of that "engagement" actually takes on Facebook, according to a report from the tech website Mashable, which said that it averages out to “less than one like over the course of the eight weeks the study was conducted.”

This could prove to be a problem for Facebook’s new “Collections” feature, an experimental Pinterest-style application the company recently rolled out in an effort to attract more brands and, presumably, more e-commerce activity to the site.

Even in Stern Agee’s less-than-rosy portrayal of the social media site, the firm noted that enhanced e-commerce capabilities such as Facebook’s new “Gifts” feature are the greatest area of opportunity for immediate growth for the company.

Facebook’s task is then to court a deeper level of engagement, rather than simply focusing on increasing its gross number of users or fans for a given page.  

“Every business has to measure what they do and make sure that it is effective. Likes can be part of that measurement, but we need to start looking beyond that a bit, and start looking in more depth at what fans are actually doing,” Riley Gibson, Napkin Labs co-founder and CEO, told Mashable. Rather than simply focusing on increasing their numbers, therefore, brands may benefit more for developing new strategies to enhance engagement of existing fans.

“If you can get fans involved, get them talking about the brand, the engagements of each of those fans gets pushed to their friends' feeds,” Gibson said. “So you can actually build more presence in the news feed by engaging your core audience.”