It's clubbing season, so pity poor Priceline.com (NASDAQ:PCLN). Last evening, it issued one of those earnings reports that exceeded expectations but, nonetheless, caused the stock to take a 12% beat-down in early trading.

What was the problem? Certainly not the top-line growth of 58% for $470 million in gross travel bookings. (Revenues were up 8% over last year's second quarter, but this doesn't accurately portray sales growth because of Priceline's new math.) The bottom line beat analysts' expectations, coming in at $0.32 per share. Whoops. That's proforma net income -- the Priceline favorite -- which excludes a gaggle of inconvenient realities. The real earnings number came to $0.29 per share, which still outpaced the prior year's quarter by 43%.

Most talking heads are blaming the firm's earnings outlook for today's sunrise spanking, but that's only part of the problem. Sure, management forecasted revenues and earnings below the Street's hopes, but it may just be lowballing. Perhaps bigger causes for concern are predictions of 20% and 25% growth for car rental days and hotel room nights. Unit bookings in these segments had been growing at 80% and 35%, respectively.

Shareholders might also want to sweat operating expenses a bit. Certain line items in have seen hefty bloat, far outstripping the growth rate of revenue. For instance, there's the 62% swell in general and administrative expenses. Also, note the much larger expenditures on advertising, which are up more than 50% to $16 million, consuming a full 30% of the quarter's gross profits.

From my seat, it points to the difficult market for online travel. How is Priceline any different than competition such as Cendant's (NYSE:CD) Cheaptickets.com, Sabre Holdings' (NYSE:TSG) Travelocity, Orbitz (NASDAQ:ORBZ), or InterActiveCorp's (NASDAQ:IACI) Expedia? Maybe, it's not. Or not different enough to matter. That makes it hard for this Fool to justify a Priceline stock purchase, despite today's fire sale.

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Fool contributor Seth Jayson books all his travel online, but he has no position in any firm mentioned. View his Fool profile here.