Priceline Group Inc (PCLN) is one of those momentum stocks that investors love. PCLN stock is one of the most expensive companies per share on Wall Street — a novelty at a price of more than $1,100 — and Priceline stock is up an impressive 600% in the last five years.

But the online travel giant has hit a patch of turbulence in 2014, with PCLN stock in the red year-to-date vs. a gain of about 9% for the S&P 500 index in the same period.

Most of that decline has come this week, with a dip of almost 10% after Priceline Group Inc. offered up weak earnings guidance.

So is this just a layover for PCLN stock amid its high-flying run? Or have Priceline earnings hinted at more trouble ahead?

Sadly for investors, I believe it’s the latter.

PCLN Stock in a Tailspin

First, some logistics: Priceline’s expensive share price has pushed out day traders and gives the company a massive institutional ownership rate of about 96% right now.

Thus, the big move down after earnings hints that the “smart money” is exiting PCLN stock big-time.

On the surface, that’s a bit of a head-scratcher. Priceline earnings beat on both the top and bottom lines, and year-over-year growth for gross bookings remained strong.

However, investors looking ahead were disappointed by weak Q4 guidance from Priceline that totaled $9.40 to $10.10 in earnings per share, significantly under the $10.91 forecast.

This is the big reason PCLN stock is selling off, and a miss that big on future guidance doesn’t bode well for bargain hunters.

Remember, Priceline stock sold off after it lowered forecasts in August despite strong profits. While revenue has increased by at least 20% a year for each of the last seven years, Priceline is becoming a victim of its own success as investors look forward to big profits despite a massive reach already.

What’s Next for Priceline Group

There are reasons to be optimistic, of course, if you’re a bull. The bottom and top lines still are growing, and clearly there is expansion ahead. A big driver of Priceline stock has been its growth through expansion and acquisition, with Priceline making inroads in Europe and recently investing half a billion bucks in Chinese travel portal Ctrip.com (CTRP). Its purchase of travel search provider Kayak is another good example of strategic growth initiatives that will keep paying off.

But competition is fierce, and not just from typical rivals like Expedia Inc. (EXPE) and the smaller portal Orbitz Worldwide Inc. (OWW). Younger players including Hipmunk, HotelTonight and Airbnb could carve out market share — or at least create growth challenges.

While Priceline Group does have a fair valuation of about 17 right now after the selloff, making it cheaper than OWW or EXPE stock, there are big headwinds ahead.

The sentiment shift after earnings and growth challenges made evident after missed guidance could hold back PCLN for some time.

Sell this underperformer — don’t bother buying Priceline Group Inc. on a dip.

Jeff Reeves is the editor of InvestorPlace.com and the author of The Frugal Investor’s Guide to Finding Great Stocks. As of this writing, he did not hold a position in any of the aforementioned securities. Write him at editor@investorplace.com or follow him on Twitter via @JeffReevesIP.