With the stock market constantly hovering near all-time highs, investors might be wondering if popular growth stocks near 52-week highs still have any room left to run. Let's take a look at three stocks that have defied fundamental gravity over the past year, and whether or not their growth stories remain intact.

Vipshop Holdings
Vipshop Holdings (NYSE:VIPS) is an online discount marketplace in China best known for its flash sales strategy. Its stock has soared more than 220% over the past 12 months, and it currently trades at a whopping 1,400 times trailing earnings. However, it also trades at 41.6 times forward earnings with a five-year PEG ratio of 0.71, which suggests that its stock price could stabilize as its earnings growth reconciles with its trailing multiples.

Wall Street is fairly bullish on Vipshop's growth prospects. The consensus estimate calls for Vipshop's full-year earnings and revenue to rise 73% and 64% between fiscal 2014 and 2015, respectively. Analyst price targets from Thomson Reuters/First Call fall between $200 to $302, suggesting that the stock has more upside than downside from current price levels.

While those numbers look great, Vipshop is still a small fish in the massive Chinese marketplace (business to consumers) industry. China Internet Watch reports that Vipshop only controlled 2.8% of this market in the second quarter of 2014, up from 1.9% a year earlier but down from 3% in the first quarter. JD.com controlled 21.2% of the market during the second quarter. Therefore, fierce competition could force Vipshop to increase marketing costs and accept lower profits per transaction, which could make it tough to prevent its slim net profit margin of 3.6% from declining.

Palo Alto Networks
Palo Alto Networks (NYSE:PANW), which sells its network security platform to service providers, businesses, and government sectors, has rallied nearly 150% over the past 12 months for two simple reasons: massive revenue growth and an unfortunate surge in data breaches worldwide.

The company's bottom line has remained in the red ever since going public in July 2012, but its full-year revenue soared 51% year over year to $598 million in fiscal 2014. Palo Alto doesn't expect that top-line growth to slow down anytime soon. It expects its first quarter revenue, which will be reported on Nov. 24, to rise 39% to 42% year over year to a range between $178 million and $182 million. Non-GAAP diluted net income is expected to come in at $0.12 per share, a 50% improvement over the $0.08 per share it posted on the same basis in the first quarter of 2014.

Although Palo Alto only controlled about 4% of the $10 billion network security market last year, its top line is growing faster than its larger rival Fortinet (NASDAQ:FTNT) and market leader Check Point Software (NASDAQ:CHKP), which controlled roughly 15% of the market:

YOY revenue growth:

Previous quarter

Most recent quarter

Palo Alto

49%

59%

Fortinet

24%

25%

Check Point

7%

8%

Source: NASDAQ, company earnings reports

While Palo Alto is certainly the most lucrative choice of the three, investors should note that all three stocks are currently trading near 52-week highs on strong investor demand for pure play network security firms.

Facebook
Shares of Facebook (NASDAQ:FB) have soared 55% over the past twelve months, giving it a trailing P/E ratio of 86. The world's largest social network repeatedly surprised investors with strong year-over-year advertising revenue growth and its smooth transition to mobile devices. During the second quarter, Facebook's advertising revenue soared 67% year-over-year to $2.68 billion, with 62% of that revenue coming from mobile platforms -- up from 41% a year earlier.  

The bears often highlight two flaws in Facebook's long-term plan -- its slowing year-over-year user growth and waning interest from teen users. Between the second quarters of 2012 and 2013, Facebook's monthly active users (MAUs) rose 21%. But between the corresponding quarters of 2013 and 2014, MAUs only climbed 14%. A recent Piper Jaffray survey also revealed that only 45% of 13-to-19-year-olds still used the site, down from 72% a year earlier.

But investors should remember that Facebook also owns two other rapidly growing platforms, Instagram and WhatsApp. Instagram, which Piper Jaffray notes that the majority of teens use instead of Facebook, saw its active users double from 100 million to 200 million between February 2013 and March 2014. WhatsApp's user base also doubled from 300 million to 600 million between August 2013 and August 2014.

And although teen use of Facebook is dropping, a recent survey from iStrategy Labs found that use among adults 25 years and older is still soaring by the double digits. This means that older users, who have comparably more spending power (and thus more advertising appeal) than younger ones can easily offset lower teen engagement numbers on the network.

Leo Sun owns shares of Facebook. The Motley Fool recommends Check Point Software Technologies and Facebook. The Motley Fool owns shares of Check Point Software Technologies and Facebook. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.