Editor's Note: This article was originally published on Real Money at 2:10 p.m. on July 18.

Facebook (FB) - Get Report has become the bellwether of the social media sector in recent years as it has expanded its reach and as competition from Twitter (TWTR) - Get Report has dissipated. However, ahead of the company's second-quarter earnings release next week, Facebook has attracted both bearish and bullish sentiment from an array of industry watchers.

Count SunTrust among the bulls. After speaking with advertisers and Facebook distribution partners, SunTrust analyst Robert Peck sees indications that the company will have above-consensus quarter-over-quarter growth for both Facebook and Instagram. The firm is forecasting 53% year-over-year ad revenue growth to $5.85 billion, including mobile revenue.

"We note that many of Facebook's distribution partners (PMDs) are pointing to overall quarter-over-quarter slightly above (Wall Street) growth (Facebook + Instagram) at +13% or better, with strong y/y performance for the Core Facebook product," Peck wrote. "Strong demand is being driven by video as well as new ad units (DPA and carousel) and incremental demand for Instagram inventory. Further, verticals such as Travel and CPG showed strong adoption in areas like new ad units and tools/targeting."

SunTrust continues to see Instagram as a key growth driver for the company. Instagram topped 500 million monthly active users and 300 million daily active users in June, according to the firm's metrics.

While users do spend two to five times more time on Facebook than Instagram, Peck wrote that Instagram could generate $3 billion in revenue and $1.98 billion in earnings before interest, taxes, depreciation and amortization, giving it a valuation on its own of about $28 billion.

However, Facebook stock -- a key holding of TheStreet'sAction Alerts PLUS charitable trust -- has underperformed since its last earnings release.

That fact, coupled with increased competition from the likes of Snapchat, has compelled Citron Research short-seller Andrew Left to turn sour on the social media company.

"We started to overshare as people," Left told Real Money's James Passeri in a Monday phone interview. "Facebook's business model was based on everyone sharing," he added. "Now everyone sharing can hurt you, and kids are learning in class that things you post can hurt you -- and to treat your name like a brand."

"People are dying for something different," Left said, emphasizing that companies like Facebook and Twitter must remain relevant to keep their engagement levels up. (Twitter is also a holding in Action Alerts PLUS.)

"Who has the most to lose? Facebook is the loser," Left said, emphasizing that "Facebook has been the beneficiary of our obsession with our phones" and that roughly 80% of Facebook's revenue is derived from mobile advertising.

And while Facebook may be at a structural risk of falling off its $320 billion market-cap perch, it's no time for short sellers to hop in until the shares fall and people re-evaluate their portfolios, Left said.

"Wait until it breaks," he added.

Left isn't the only high-profile investor losing faith in Facebook. Real Money Pro's Doug Kass penned a piece Monday morning explaining why he is shorting Facebook ahead of next week's results.

"With the market extended to the upside, I'm looking for some short rentals. So, let's make this week's Trade of the Week a short of Facebook at $117.05," Kass wrote. "This is mostly a technical call. Facebook is approaching the $118.72 level, which is where the shares recently broke down. That makes that the resistance level in my book."

Back on the bull side, the Action Alerts PLUS team maintains its positive outlook on the social media company.

"If the sheer magnitude of Facebook's clout doesn't convince you, the continued acceleration of its active-user growth and industry-high engagement levels continue to drive network effects, while its valuable trove of data enhances targeting capabilities, all of which provide unmatched value to advertisers," co-portfolio managers Jim Cramer and Jack Mohr wrote Friday.

Despite that vote of confidence, the charitable trust did trim its position in Facebook by 200 shares Monday. Representing more than 5.6% of its portfolio, Facebook was AAP's largest percentage holding. Following the trade, Facebook now represents 4.76% of the overall portfolio.

"The move is nothing more than an attempt to take advantage of the opportunity to ring the register modestly on parabolic profits, rather than succumb to sheer greed," Cramer and Mohr wrote Monday.

While Left is betting on some of Facebook's competitors, Action Alerts PLUS senior analyst Scott Berman sees Left's position and the portfolio's position as the difference between a trader and a long-term investor. Even if Facebook was in danger of losing a significant number of users to its competitors, the company's ad revenue would suffer minimally, Berman said.

"(Left) has highlighted Snapchat's growth as one area of concern for FB and the general entry of new players that can take away ad revenue. But don't forget that FB boasts 1.6 billion MAUs and also has WhatsApp (1 billion MAU), Messenger (900 million MAU), and Instagram (500 million MAU and growing faster than previous 100 mill that were added)," Berman said in an email exchange.

"That's a lot of eyeballs and marketers are going to want to reach all of these people. So let's say ad revenue allocation to FB's core platform is pressured (which we don't foresee happening), a lot of that revenue would be captured by FB's subsidiaries anyway. And we don't think that will happen, but rather marketers will have to allocate funds to all of these platforms to take advantage of their different use cases and value propositions," he said.

A lot of investor questions will be answered once the company releases its second-quarter results July 27. In the meantime, investors with differing opinions are either positioning themselves to benefit from a coming dip, or continue to reap rewards from Facebook's upward trajectory.

"For instance, Doug Kass highlighted FB as a short idea for the week, but is making his trade from more of an opportunistic point of view rather than from a fundamentals point of view," Berman concluded. "Bottom line is that Kass shouldn't necessarily be considered a bull or a bear. Based on this recent trade idea, he is more likely just looking to cash in on a quick market move that he expects to be coming."

-- Real Money's James Passeri contributed to this report.