Although we don't believe in timing the market or panicking over market movements, we do like to keep an eye on big changes -- just in case they're material to our investing thesis.

What: Shares of TripAdvisor (NASDAQ:TRIP) fell as much as 11% Thursday after the travel-recommendation website came up short on the bottom line in its second-quarter earnings report.

So what: Sales increased by a brisk 31% to $323 million, as click-based advertising, which makes up the majority of sales, grew by 28%. That revenue figure topped the expectation of $321.7 million, but marketing costs rose more than 50% and ate into profits: Earnings per share improved only from $0.52 to $0.55, missing the consensus estimate of $0.61. 

Now what: The stock's decline probably owes as much to its recent gains and high valuation as it does to the earnings miss. TripAdvisor shares have more than tripled in value since the company was spun off from Expedia at the end of 2011; at a P/E near 70, the stock may be deserving of a correction. While 30% growth is impressive, this company competes directly with Yelp and other online travel services including priceline.com, and would seem to have little sustainable competitive advantage. The jump in marketing expenses may also show that the travel service is having difficulty maintaining its top-line growth. Considering those issues, I wouldn't be surprised to see the stock fall further.