Other competitors in the services sector include: Orbitz Worldwide (OWW), Expedia (EXPE), and Travelzoo Inc. (TZOO).

FORBES: Earnings Preview: priceline.com

Orbitz Worldwide, Inc. (OWW), which is highly leveraged to the U.S. airline industry, has been crushed to the tune of 37 percent this year.

FORBES: Playing The Fire In Priceline Without Getting Burned

Orbitz Worldwide (OWW) is expected to report poor second quarter earnings on Wednesday, August 8, 2012 with analysts expecting a 55.6% drop in earnings from a year ago.

FORBES: Earnings Preview: Orbitz Worldwide

Think again: Expedia ( EXPE) exited the meta-search market, spinning off TripAdvisor ( TRIP) in an IPO last year, when Priceline and Orbitz ( OWW) balked at disclosing advertising budgets to Expedia.

FORBES: Connect

Orbitz ( OWW - news - people ), but the set-price business has been growing three times as fast and now represents more than half of revenue and two-thirds of profits.

FORBES: On The Cover/Top Stories

One further worry is the possibility that the selling in Priceline could be hinting at the potential for further, intermediate-term weakness in the group, with stocks like Expedia (NASDAQ: EXPE) and Orbitz Worldwide (NYSE: OWW) appearing increasingly vulnerable.

FORBES: The Return of the Negotiator and the Revival of Priceline

Once William Shatner returns to commercials, consumers may begin to remember why Priceline was the leader in online travel bookings and feel confident in using the service once again, rather than traveling through competitors like Expedia (NASDAQ: EXPE), Orbitz (NYSE: OWW), Travelzoo (NASDAQ: TZOO) and Ctrip.com (NASDAQ: CTRP), all of which have been trending upward recently (with the exception of Orbitz, which traded down seven percent during Wednesday trading).

FORBES: Priceline Customers: Bring Back the Negotiator!