When Snap Inc. (SNAP) - Get Snap, Inc. Class A Report made its public debut last Thursday, Wall Street's roaring enthusiasm for the fast-growing tech company catapulted the stock 44% higher. 

That enthusiasm now appears to be fizzling out as shares of Snapchat's parent company fell almost 10% to $21.44 on Tuesday, after falling 12% on Monday to below its opening price of $24 per share. 

And while it's not unheard of for recently listed tech companies to falter in their first few weeks of trading (Facebook's (FB) - Get Facebook, Inc. Class A Report stock fell below its $42 opening price in the second day of trading after its 2014 IPO), Snap's stock performance does little to quiet the voices of those who have become bearish about its growth prospects. Of the eight analysts that currently cover Snap, none of them have a Buy rating on it and two have a Sell rating, according to FactSet

Bearish analysts have argued that Snap is overvalued for a company that has yet to turn a profit, may continue seeing decelerating user growth and is weighed down by cloud service costs. These concerns are likely playing a part in the stock's recent decline, said Aegis Capital analyst Victor Anthony, who has a Hold rating and $22 price target on shares of Snap. 

App tracking data shows that Snap's daily active user (DAU) growth fell in the first two months of the fiscal 2017 first quarter, Anthony said, demonstrating that Facebook's Instagram is a persistent threat to the disappearing message app.

Facebook launched Instagram Stories last August, a near copycat of Snapchat Stories that allows users to post photos and videos lasting for up to 24 hours. Like Snapchat Stories, Instagram Stories incorporate unique geofilters, lenses and stickers to personalize posts. 

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Snap noted in its S-1 filing with the SEC that DAUs were up 48% year-over-year in the fourth quarter of 2016, while Anthony said its app tracking data shows that number was probably up closer to 15% year-over-year. Meanwhile, fiscal first-quarter DAU growth was likely around 3% year-over-year, according to the app data, he added.

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"The tracking data suggests that the accelerated growth of net adds in December, though in part due to seasonality, did not continue into the new year," Anthony explained, noting that Instagram's DAU growth was "almost double" that of Snapchat's in the fiscal first quarter. 

Short sellers, or those betting on a decline in the stock, could also be putting pressure on shares, Anthony said. 

Needham analyst Laura Martin laid out seven different areas that could stand in the way of Snap seeing explosive growth, such as the ease with which Facebook has been able to replicate features of Snapchat. The risks make Snap a "lottery-like" stock, Martin explained. 

"Sometimes lottery tickets do pay off, but a close scrutiny of Snap's fundamentals uncovers [some risks]," Martin added. 

Cloud communications platform Twilio  (TWLO) - Get Twilio, Inc. Class A Report became a victim of short sellers in the months following its IPO last June. Twilio started off trading more than 90% above its IPO price and eventually increased nearly fivefold. But its stock began trading lower as short interest grew and the company announced it would sell additional shares last October. 

Twilio's short interest rose to $80 million in the first week after its IPO filing, which was 20% of the initial offering, according to financial analytics firm S3 Partners. 

It's likely too early to tell if short selling is playing a major role in Snap's stock decline, said Ihor Dusaniwsky, head of research at S3 Partners. Snap has been a highly active stock in its first few days of trading, with approximately 2.27 million shares changing hands so far on Thursday. 

"The vast majority of these shares traded are from long holders selling their positions in order to realize some of the profits they earned since the IPO," Dusaniwsky explained. 

Snap could face additional pressures if a group of institutional investors have their way. The group is meeting with officials from S&P Dow Jones Indices and MSCI Inc. MSCI to exclude Snap and other companies that sell non-voting shares from joining their indices, according to the Journal. As part of its IPO, Snap issued Class A shares with no voting rights.

If Snap isn't included on a major index like the S&P 500, it could miss out on an additional rally. Managers of stock index portfolios typically rush to buy up shares of a recently added company, the Journal reports.